Apparatus for manufacturing multilayer polymeric films

ABSTRACT

A feedblock including a first packet creator that forms a first packet including a first plurality of polymeric layers, the first plurality of layers including at least four first individual polymeric layers; and a second packet creator that forms a second packet including a second plurality of polymeric layers, the second plurality of layers including at least four second individual polymeric layers, wherein the first and second packet creators are configured such that, for each packet creator, respective individual polymeric layers of the plurality of polymeric layers are formed at approximately the same time. The feedblock may include a packet combiner that receives and combines the first and second primary packets to form a multilayer stream. In some examples, at least one of the first and second primary packets may be spread in the cross-web direction prior to being combined with one another.

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. patent application Ser. No.13/102,326, filed May 6, 2011, which claims the benefit of U.S.Provisional Patent Application No. 61/332,382, filed on May 7, 2010, thedisclosure of which is incorporated by reference herein in theirentirety.

TECHNICAL FIELD

The invention relates to multilayer films and, in particular,apparatuses and techniques for making multilayer polymeric films.

BACKGROUND

Multilayer polymeric films may exhibit a wide range of optical andphysical properties, and may be utilized in a variety of optical andnon-optical applications. The optical and physical properties of amultilayer film may depend on a number of variables, including the typeof polymeric materials used for the individual layers, the overallnumber of individual layers of a film, and/or the layer thicknessprofile of a film. As a result, the properties of a multilayer film maybe tailored by precisely controlling one or more of these variablesduring the film manufacturing process.

SUMMARY

In general, the present disclosure relates to apparatuses and techniquesthat may be utilized to manufacture multilayer films, such as multilayerpolymeric films having multiple individual polymeric layers. In someembodiments, a feedblock apparatus used to generate a multilayer flowstream may include a packet creator section that includes two or morepacket creators. Each packet creator may be configured to generate aseparate primary packet having a plurality of individual layers. In someembodiments, each of the primary packets generated by a packet creatormay be generated independently of one another. For example, the numberof layers, the layer thickness profile, and/or the type of layermaterial in a packet may be substantially independent of one or more ofthe other primary packets generated in the packet creator section.

The feedblock apparatus may further include a packet combiner which mayreceive the two or more primary packets from the packet creator sectionand then combine the primary packets into a single multilayer flowstream. In some embodiments, the packet combiner may change theorientation of the received primary packets such that at least a portionof the respective packets are stacked when combined with one another. Bycombining the at least two primary packets, the multilayer flow streamexiting the packet combiner may include a plurality of layers that isgreater than the number of layers in either primary packet generated bythe packet creator section. For example, when at least a portion of therespective packets are stacked when combined with one another, at leasta portion of the resulting multilayer flow stream may include a numberof individual layers greater than or equal to the sum of individualslayers from each primary packet.

An apparatus for manufacturing multilayer polymeric films may beconfigured to separately receive two or more packets, e.g., from afeedblock including multiple packet creators, and then combine thepackets to form a single multilayer flow stream. The multilayer flowstream may be further processed in some examples to form a multilayeroptical film. In some embodiments, the apparatus may be configured toindividually spread the packets in the cross-web direction prior tocombining the packets to form the multilayer stream. In this manner, thespreading of the packets in the cross-web direction within the apparatusmay be designed and controlled independently of one another prior tobeing combined into the multilayer flow stream. Additionally oralternatively, the multilayer flow stream may be spread in the cross-webdirection after being formed by the combination of the individualpackets.

In one embodiment, the disclosure is directed to a feedblock comprisinga first packet creator that forms a first packet including a firstplurality of polymeric layers, the first plurality of layers includingat least four first individual polymeric layers; a second packet creatorthat forms a second packet including a second plurality of polymericlayers, the second plurality of layers including at least four secondindividual polymeric layers, wherein the first packet creator isconfigured such that the first individual polymeric layers are formed atapproximately the same time as one another, and the second packetcreator is configured such that the second individual polymeric layersare formed at approximately the same time as one another. The packetcombiner comprises a first channel that receives the first packet fromthe first packet creator, and a second channel that receives the secondpacket from the second packet creator, wherein the first channel and thesecond channel are configured to combine the first and second packets toform a multilayer stream including the first plurality of polymericlayers and second plurality of polymeric layers.

In another embodiment, the disclosure is directed to a method formanufacturing a multilayer article, the method comprising forming afirst packet including a first plurality of polymeric layers via a firstpacket creator, the first plurality of polymeric layers including atleast four first individual polymeric layers; forming a second packetincluding a second plurality of polymeric layers via a second packetcreator, the second plurality of polymeric layers including at leastfour second individual polymeric layers, wherein the first individualpolymeric layers are formed at approximately the same time as oneanother, and the second individual polymeric layers are formed at thesame time as one another; and combining the first packet and the secondpacket via a packet combining section to form a multilayer flow streamincluding the first plurality of polymeric layers and second pluralityof polymeric layers.

In another embodiment, the disclosure is directed to a feedblockcomprising means for forming a first packet including a first pluralityof polymeric layers, the first plurality of polymeric layers includingat least four first individual polymeric layers; means for forming asecond packet including a second plurality of polymeric layers, thesecond plurality of polymeric layers including at least four secondindividual polymeric layers, wherein the first creator is configuredsuch that first individual polymeric layers are formed at approximatelythe same time as one another, and the second packet creator isconfigured such that the second individual polymeric layers are formedat approximately the same time as one another; and means for combiningthe first packet and the second packet to form a multilayer flow streamincluding the first plurality of polymeric layers and second pluralityof polymeric layers.

In another embodiment, the disclosure is directed to an assembly formanufacturing a multilayer film, the assembly comprising a first flowchannel configured to received a first primary packet, the first primarypacket including a first plurality of polymeric layers; and a secondflow channel configured to received a second primary packet, the secondprimary packet including second plurality of polymeric layers, whereinthe first channel and the second channel are configured to spread atleast one of the first and second packets in a cross-web direction and,after spreading the at least one of the first and second primary packetsin the cross-web direction, combine the first and second primary packetsto form a multilayer flow stream including the first and secondplurality of polymeric layers.

In another embodiment, the disclosure is directed to a method comprisingreceiving a first primary packet via a first flow channel, the firstprimary packet including a first plurality of polymeric layers;receiving a second primary packet via a second flow channel, the secondpacket including second plurality of polymeric layers; spreading atleast one of the first primary packet and second primary packet in across-web direction; and combining the first primary packet and secondprimary packet with one another after spreading at least one of thefirst packet and second packet in the cross-web direction to form amultilayer flow including the first and second plurality of polymericlayers.

In another embodiment, the disclosure is directed to an assembly formanufacturing a multilayer film, the assembly comprising means forreceiving a first primary packet via a first flow channel, the firstprimary packet including a first plurality of polymeric layers; meansfor receiving a second primary packet via a second flow channel, thesecond packet including second plurality of polymeric layers; means forspreading at least one of the first primary packet and second primarypacket in a cross-web direction; and means for combining the firstprimary packet and second primary packet with one another afterspreading at least one of the first packet and second packet in thecross-web direction to form a multilayer flow including the first andsecond plurality of polymeric layers.

The details of one or more embodiments of the invention are set forth inthe accompanying drawings and the description below. Other features,objects, and advantages of the invention will be apparent from thedescription and drawings, and from the claims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram illustrating an example film line that maybe used to manufacture a multilayer film.

FIGS. 2A and 2B are conceptual diagrams illustrating an examplefeedblock.

FIGS. 3A-C are example cross-sectional views illustrating feedblock 50along line A-A in FIG. 2A.

FIGS. 4A and 4B are conceptual diagrams illustrating various aspects ofan example feedblock.

FIGS. 5A-5C are conceptual diagrams illustrating various aspects of anexample feedblock.

FIGS. 6A-6L are conceptual diagrams illustrating various examplefeedblock configurations.

FIG. 7 is a conceptual diagram illustrating an example multilayer flowstream.

FIG. 8 is a conceptual diagram illustrating an example packet combinerand extrusion die.

FIG. 9 is a conceptual diagram illustrating an example cross-sectionalview of the multilayer flow in the example extrusion die shown in FIG. 8along cross-section C-C.

FIG. 10 is a conceptual diagram illustrating example packet transporterand extrusion die.

FIG. 11 is a conceptual diagram illustrating another example packettransporter and extrusion die.

FIG. 12 is a conceptual diagram illustrating an example cross-sectionalview of the multilayer flow in the example extrusion die shown in FIG.11 along cross-section D-D.

FIG. 13 is a conceptual diagram illustrating another example packettransporter and extrusion die.

FIG. 14 is a conceptual diagram illustrating an example cross-sectionalview of the multilayer flow in the example extrusion die shown in FIG.13 along cross-section E-E.

FIG. 15 is a conceptual diagram illustrating another example packettransporter and extrusion die.

FIGS. 16 and 17 are conceptual diagrams illustrating examplecross-sectional views of the multilayer flow in the example extrusiondie shown in FIG. 15 along cross-section F-F

DETAILED DESCRIPTION

In general, the present disclosure relates to apparatuses and techniquesthat may be utilized to make multilayer films, such as multilayerpolymeric films that have multiple individual polymeric layers. Forpurposes of illustration, embodiments of the disclosure are generallydescribed with regard to manufacturing multilayer optical polymericfilms. However, it is recognized that embodiments of the disclosure arenot limited to optical films. For example, embodiments of the disclosuremay be useful for manufacturing any multilayer film in which anapparatus, such as a feedblock, receives one or more polymeric filmmaterials to create a multilayer flow stream having individual polymericlayers that may be further processed into a multilayer film. Examples ofsuch multilayer polymeric films may include both optical and non-opticalpolymeric films.

A multilayer polymeric film may include a plurality of individual layerseach formed of one or more types of polymeric materials. For example,certain multilayer optical films may include hundreds of individualpolymeric layers alternating between high and low index polymericmaterials. The formation of such polymeric layers may be accomplishedvia a feedblock apparatus that receives suitable polymeric materials,generally in the form of polymeric melt streams, and orients thepolymeric materials into a multilayer polymeric flow stream including astack of individual layers. After exiting a feedblock, the multilayerflow stream may then be further processed within a film line to generatea multilayer optical film. Examples of feedblocks and film linesconfigured to manufacture multilayer optical films are described, e.g.,in U.S. Pat. No. 6,783,349 to Neavin et al., titled “Apparatus forMaking Multilayer Optical Films,” which is incorporated herein byreference in its entirety.

The multilayer flow stream resulting from the initial orientation ofpolymeric materials into stacked individual layers by a feedblock may bereferred to as a primary or parent packet. Conventionally, the number ofindividual layers of the multilayer flow stream exiting a feedblock isapproximately equal to that of the primary packet generated by thefeedblock. Since one or more of the physical and/or optical propertiesof a multilayer film may depend on the number of individual polymericlayers in the film, it may be desirable to control the number of layerspossessed by a primary packet.

However, the number of individual polymeric layers capable of beingpossessed by a primary packet generated in a feedblock may be limiteddue to a number of factors. Example factors may include but are notlimited to feedblock design and/or practical considerations such as thephysical dimension, weight and/or cost of a feedblock capable ofgenerating a desired number of polymeric layers. Accordingly, it may notalways be feasible for a feedblock to generate a primary packet having anumber of individual layers greater than or equal to the number oflayers that are desired for types of multilayer films.

Furthermore, in addition to controlling the number of individual layersof a multilayer optical film, it may also be desirable to preciselycontrol the thickness of the individual layers that make up themultilayer optical film, the combination of which may be generallyreferred to as a layer thickness profile. For example, one or morephysical and/or optical properties of a multilayer optical film may bedependent on the layer thickness profile of the multilayer optical film,in addition to the number of individual layers in the film. In somecases, it may be desirable for a multilayer film to possess a layerthickness profile such that there is a monotonic variation or gradientof layer thicknesses throughout a multilayer film. Deviation of thelayer thickness within a multilayer optical film from a target layerthickness profile may result in degradation of the film's performance.

Accordingly, it is generally desirable to precisely control the layerthickness profile of the multilayer flow stream generated by afeedblock, and a variety of techniques may be implemented in themanufacturing process to at least partially provide for control or“tuning” of the layer thickness profile in the multilayer flow stream.For example, as described in U.S. Pat. No. 6,783,349 to Neavin et al.,one or more axial rod heaters located proximate to conduits that deliverpolymeric melt streams within a feedblock may be used to supplyadditional heat to the conduits to locally lower the polymeric viscosityand promote additional flow within the conduits. In such cases, theamount of heat added per location may be adjusted and controlled toobtain desirable layer thickness and/or optical spectra of themultilayer film that is manufactured from the primary packet generatedby the feedblock.

When the number of individual polymeric layers required for a multilayeroptical film exceeds the practical number of layers that can be directlygenerated by a feedblock, a layer multiplier device (which may also bereferred to as a interfacial surface generator) may be used to increasethe number of layers in the multilayer flow stream that forms themultilayer film. The multiplier device may receive the multilayer flowstream from a feedblock, which has a number of layers approximatelyequal to that of the parent packet created by the feedblock, and splitthe flow stream into two or more sub-streams. Each of these sub-streamsmay be referred to as secondary packets. The multiplier device may thenreorient the two or more secondary packets by stacking the packets ontop of one another and then combining the secondary packet to generate amultilayer flow stream with an increased number of individual layers.This process may be repeated on the resulting flow stream until amultilayer flow stream with the desired number of individual layer isachieved.

In some multilayer optical film applications, a multiplier device may berequired to split and divide the layers according to a ratio ofthicknesses between the secondary packets. The ratio of mass flow ofsecondary packet “A” to secondary packet “B” may be referred to as themultiplication ratio. In some examples, multiplication ratios may rangefrom approximately 1.0 to approximately 2.0. To achieve desiredmultiplication ratios between packets using a multiplier device, thephysical dimensions of a multiplier may be designed to precisely controlthe flow channel resistance so that the resulting ratio of the mass flowrates through the channels is equal to the target multiplication ratiodesired.

While in some situations the described approach of generating a singleparent packet with multiple layers within a feedblock and thenincreasing the number of layers using a multiplier device may besuitable for manufacturing some multilayer optical films, in some cases,such a process may present one or more undesirable limitations. Forexample, because each non-primary packet, e.g., secondary packets,descends from the single parent packet generated in the feedblock, thenumber of layers is generally the same in each non-primary packet.Therefore, to such an extent, the exact number of layers present in amultilayer optical film is highly dependent on the number of layerspresent in the primary packet generated by a feedblock.

Furthermore, as another example, optimal multiplier device design may beperformed assuming specific polymeric resins properties, such as, e.g.,viscosity, and specific process conditions, such as, e.g., temperatureand flow rate. As a result, if different polymers are used or processingconditions differ from the assumptions used in the original design, theresulting multiplication ratio between packets will likely deviate fromthe original target ratio. Moreover, if a new multiplication ratio isdesired, the flow channels of the multiplier device may need to bemechanically altered, e.g., machined, to obtain the correct flowresistances that correspond to the desired multiplication ratio.

As another example, errors in the layer thickness profile that occur inthe primary packet are multiplied along with the layers and are presentin each of the secondary packets. Moreover, during the multiplicationprocess, the amplitude of the error is often increased relative to thenumber of times a packet is multiplied, and the zone of influence fromthe error in the cross-web direction may be increased as well.

As still another example, multiplier device design capabilities may notallow for any means to compensate the multiplication ratio forvariations in process conditions or lot-to-lot variations in resinproperties during production of multilayer optical films. As a result,there may be deviations in a manufactured multilayer film from a targetspectrum due to optical leaks between packets and/or due to overlaps inthe layer thickness of respective packets. Furthermore, typicalapproaches to multiplier design may make it difficult to obtain flowgeometries that simultaneously achieve both the target multiplicationratio as well as providing uniform spreading of layer in the cross-webdirection.

Embodiments of the disclosure may address one or more of the limitationsidentified above. As will be described in the greater detail below, insome embodiments, a feedblock may include a packet creator sectionconfigured to generate multiple primary packets. The primary packets maybe generated independently of one another, which may allow for the oneor more properties of each primary packet to be controlled or “tuned”independently of one another. After the primary packets are generated,the primary packets may be combined with one another in a packetcombiner to create a multilayer flow stream. In this manner, in someembodiments, the feedblock may create a multilayer flow stream that hasa number of individual layers greater than the number feasible for afeedblock to generate in a single primary packet.

FIG. 1 is a schematic diagram illustrating an example film line 10 whichmay be used to manufacture a multilayer polymeric film. In general, filmline 10 may be configured to receive one or more polymeric materials andprocess the polymeric materials to form a multilayer polymeric film,such as, e.g., a multilayer optical film, in which the individual layersof the film include the one or more polymeric materials.

In the example of FIG. 1, film line 10 includes first extruder 12,second extruder 14, feedblock 16, multiplier 18, extrusion die 20,casting wheel 22, orienter 24, and windup roll 26. In the embodimentshown, film line 10 is configured to manufacture a multilayer filmhaving individual polymeric layers generally including either firstpolymeric material 28 or second polymeric material 30. However, as willbe explained below, embodiments of the disclosure are not limited toproducing a multilayer film having a first polymeric and secondpolymeric, but instead may include more than two polymers in someexamples.

As configured, first polymeric material 28 and second polymeric material30 may be heated to a temperature equal to or greater than theirprocessing temperature, e.g. melting and/or glass transitiontemperature, via first extruder 12 and second extruder 14, respectively,and fed into feedblock 16. Feedblock 16 processes first polymericmaterial 28 and second polymeric material 30 to form multilayer flowstream 32 that includes multiple individual layers of first material 28and second material 30.

As multilayer flow stream 32 exits feedblock 16, stream 32 mayoptionally be fed into layer multiplier 18. Multiplier 18 splitsmultilayer flow stream 32 into two or more sub-streams, i.e., secondarypackets, and then may recombine two or more of the respectivesub-streams after stacking one or more sub-streams atop anothersub-stream to multiply the number of layers in multilayer flow stream 32into a greater number of layers in multilayer flow stream 42. In otherembodiments, multiplier 18 may not be utilized in film line 10.

From multiplier 18, multilayer flow stream 42 enters film extrusion die20. Extrudate 44 from film extrusion die 20, which is typically in meltform, is cooled on casting wheel 22, which rotates past one or morepinning wires or bands to pin extrudate 44 to casting wheel 22. In somecases, multilayer flow stream 42 may include one or more skin layers.

From casting wheel 22, film 46 may be oriented by orienter 24. Forexample, orienter 24 may include a length orienter, such as pull rolls,that may stretch film 46 in the longitudinal (machine) direction. Asanother example, orienter 24 may additionally or alternatively include atenter that may stretch film 46 in a transverse (cross-web) direction,or may stretch film 24 bi-axially. Film 46 may be stretched by theorienters according to appropriate stretch ratios depending on theproperties desired for film 48. Film 48 may then be collected fromorienter 24 on windup roll 26.

Still referring to FIG. 1, feedblock 16 includes packet creator section34 and packet combiner 36. Packet creator section 34 includes firstpacket creator 35 and second packet creator 37. As will be described infurther detail below, each packet creator may be configured toindependently generate a single primary packet, i.e., each individualpacket creator generates a single primary packet corresponding toindividual primary packets 38 and 40 in FIG. 1. Each primary packet 38and 40 may include a plurality of individual polymeric layersalternating between first polymeric material 28 and second polymericmaterial 30. In some embodiments, packet creator section 34 may includemore than two packet creators, such as, e.g., three, four, or more thanfour packet creators, each of which are configured to generate a singleprimary packet. Accordingly, feedblock 16 is capable of creatingmultiple primary packets rather than just one primary packet, asdescribed above. In examples in which primary packets 38 and 40 includecommon polymeric material, first and second packet creators 35 and 37may be supplied with resin from individual extruders specific torespective packet creators, or a common extruder may supply the likeresin to both of packet creators 35 and 37.

Once generated from first material 28 and second material 30 via packetcreator section 34, primary packets 38 and 40 may be received by packetcombiner 36. As will be described in further detail below, packetcombiner 36 may combine primary packets 38 and 40 into a singlemultilayer stream 32. For example, packet combiner 36 may receivepackets 38 and 40 from packet creator section 34 and then redirect theflow of one or both of packets 38 and 40 so that they may be suitablycombined into a single multilayer stream 32. Depending on the desiredamount of layers in the multilayer film, multilayer stream 32 may beoptionally processed by multiplier 18, as shown in FIG. 1, or fed toextrusion die 20 without being processed by multiplier 18.

In some embodiments, packet combiner 36 may combine packets 38 and 40 byreorienting the flow of the respective packets relative to one anotherother such that at least a portion of the respective primary packets arestacked when combined by combiner 36. If at least a portion of packets38 and 40 are stacked when combined with one another, then at least aportion of the resulting multilayer stream 32 includes a total number ofindividual layers approximately equal to that of the sum of the numberof individual polymeric layers in packets 38 and 40. An example of amultilayer flow stream resulting from the combination of packets in asubstantially fully stacked configuration is further described withrespect to FIG. 7.

By combining the packets 38 and 40, the number of individual layers inthe stacked portion of multilayer stream 32 created by feedblock 16 maybe greater than either of primary packets 38 and 40 individually evenwithout the use of multiplier 18. In some embodiments, if the number ofindividual polymeric layers in flow stream 32 is suitable for a desiredfilm being manufactured, then film line 10 may not require the use ofmultiplier 18. Instead, multilayer flow stream 32 may be processed byextrusion die 20 without layer multiplication via multiplier 18. Inother cases, the number of times that multilayer flow stream 32 must beprocessed by multiplier 18 to produce a multilayer flow stream having adesired number of layers is reduced by generating more than one primarypackets in feedblock 16 and then combining them into multilayer flowstream 32.

In some examples, multilayer stream 32 may include one or moreadditional layers besides that of packets 38 and 40. For example, inpacket creator section 34, relatively thick protective boundary layersof one or more of the polymers used to form the primary packets 38 and40 may be added in first packet creator 35 and/or second packet creator37 to primary packets 38 and 40, and these may later become skin layersin film 46. In another example, one or more skin layers may be added topacket 38 and/or packet 40 within packet combiner 36 prior to the packet38 and packet 40 being combined. Such skin layer(s) may be added afterpacket 38 and packet 40 are combined to form multilayer flow stream 32.Additionally or alternatively, a core layer may be added such that thecore layer separates packet 38 and packet 40 in multilayer stream 32.Such skin layers may be made of one or both of the same polymers usedfor the packets 38, 40, or they may be made of different polymers, fromadditional extruders (not shown).

In some examples, prior to being combined with one another to formmultilayer stream 32, one or more of packet 38, packet 40 or anyadditional layer streams may be spread in the cross-web direction, e.g.,via spreading manifold. Additionally or alternatively, multilayer stream32 may be spread in the cross-web after being formed via the combinationof packet 38 and packet 40, as well as any other additional layerstream.

FIGS. 2A and 2B are conceptual diagrams illustrating example feedblock50. Feedblock 50 may be used as feedblock 16 in a film line configuredto manufacture multilayer polymeric films, such as film line 10 ofFIG. 1. For example, feedblock 50 may receive polymeric materials fromone or more extruders and generate a multilayer flow stream outputincluding the received polymeric materials as individual layers, aspreviously described. As shown, feedblock 50 includes packet creatorsection 52 and packet combiner 54, which act in combination to generatethe described multilayer flow stream output from the received polymericmaterials.

Referring to FIG. 2A, packet creator section 52 includes first packetcreator 56 within housing 57, and second packet creator 58 withinhousing 59. First packet creator 56 and second packet creator 58 areeach configured to independently generate a single primary packet. Asshown, after first packet creator 56 and second packet creator 58generate their respective individual primary packets, packet combiner 54receives each primary packets and combines them into a single multilayerflow stream.

First packet creator 56 includes first flow channel 60 a, second flowchannel 62 a, first plurality of conduits 64 a, second plurality ofconduits 66 a (not shown in FIG. 2A), slot die section 68 a, thermaltuning mechanisms 70 a and 72 a, and compression section 74 a.Similarly, second packet creator 58 includes first flow channel 60 b,second flow channel 62 b, first plurality of conduits 64 b, secondplurality of conduits 66 b (not shown in FIG. 2A), slot die section 68b, thermal tuning mechanisms 70 b and 72 b, and compression section 74b.

With regard to first packet creator 56, first flow channel 60 a andsecond flow channel 62 a are in fluid communication with one or moreextruders (not shown) which supply appropriate polymeric materials tothe respective flow channels. In the example shown, first flow channel60 a may receive a first polymeric material in the form of resin from afirst extruder (not shown) and second flow channel 62 a may receive asecond polymeric material from a second extruder (not shown).

First flow channel 60 a is also in fluid communication with plurality offirst conduits 64 a, and second flow channel 62 a is also in fluidcommunication with plurality of second conduits 66 a. As illustrated inFIG. 2B, plurality of first conduits 64 a includes seven individualfirst conduits and plurality of second conduits 66 a includes sixindividual second conduits. Each of the respective individual conduitsmay correspond to an individual polymeric layer of the plurality ofpolymeric layers in the primary packet generated by first packet creator56. Accordingly, in the example of FIGS. 2A and 2B, first packet creator56 is configured to generate a primary packet having a total of thirteenindividual polymeric layers, with seven of the polymeric layersincluding the first polymeric material and six of the polymeric layersincluding the second polymeric material. However, as will be furtherdescribed below, the number of individual layers of a primary packetgenerated by a packet creator is not limited to such a number.

Each of the individual conduits in the plurality of first conduits 64 aare in fluid communication with portions of slot die section 68 a, andeach of the individual conduits in the plurality of second conduits 66 aare also in fluid communication with portions of slot die section 68 a.Accordingly, the first polymeric material received by first flow channel60 a may be fed to the corresponding portions of slot die section 68 avia plurality of first conduits 64 a. Likewise, the second polymericmaterial received by the second flow channel 62 a may be fed to thecorresponding portions of slot die section 68 a via plurality of secondconduits 66 a. Although plurality of first and second conduits 64 a and66 a are shown in FIG. 2A connecting first and second flow channels 60 aand 62 a to slot die section 68 a in a two section, “L” shapedconfiguration, embodiments are not limited as such. For example, in someembodiments, first and second conduits 64 a and 66 a may connect firstand second flow channels 60 a and 62 a to slot die section 68 a via asingle section with a diagonal configuration. Examples exhibiting adiagonal configuration for the first and second flow conduits of firstand second packet creator sections are illustrated in FIGS. 6C and 6H,which will be described further below.

In some embodiments, the geometry of the respective flow channels 60 aand 62 a may be designed to influence the layer thickness distributionof the primary packet generated by first packet creator 56. For example,the cross-sectional area of flow channels 60 a and 62 a may remainconstant or can change, e.g., increase or decrease in area, to providean appropriate pressure gradient, and the pressure gradient provided bythe cross-sectional area of flow channels 60 a and 62 a may affect thelayer thickness distribution of the primary packet generated by firstpacket creator 56.

Optionally, residing proximate to plurality of conduits 64 a and 66 aare thermal tuning mechanisms 70 a and 72 a. In the example shown,thermal tuning mechanisms 70 a and 72 a include one or more axial rodheaters that are used to selectively provide heat to the polymericmaterial flowing in plurality of conduits 64 a and 66 a. If desired,temperature can be varied in zones along the length of the axial rodheater. In this manner, the flow rate of a polymeric material throughone or more conduits of plurality of conduits 64 a and 66 a can beadjusted according to the amount of heat being provided by thermaltuning mechanisms 70 a and 72 a, thereby influencing the thickness ofindividual layers in the primary packet generated by first packetcreator 56.

Slot die section 68 a is configured to receive the first and secondpolymeric materials from plurality of first conduits 64 a and pluralityof second conduits 66 a, respectively. In some embodiments, theindividual layers of the primary packet may be formed within slot diesection 68 a. Slot die section 68 a may include an expansion manifoldsection configured to receive the polymeric material from the respectiveplurality of conduits 64 a and 66 a and spread the polymeric material inthe width direction (x-direction) of slot die section 68 a toapproximately the desired packet width. Slot die section 68 a also mayinclude a slot section that receives the polymeric material from theexpansion manifold section, and further assists in forming theindividual polymeric layers from that polymeric material. By the timethe polymeric materials exit slot die section 68 a, the individuallayers that make up the plurality of layers of the first primary packetgenerated by first packet creator 56 are substantially formed, with themajor plane of the layers extending in approximately the cross-webdirection (x-direction), i.e., the layers are stacked in approximatelythe y-direction as indicated in FIG. 2B.

As illustrated in FIG. 2B, the individual conduits of the plurality offirst conduits 64 a are interleaved along the depth (in the y-direction)of slot die section 68 a with the individual conduits of the pluralityof second conduits 66 a. As a result, the primary packet generated byfirst packet creator 56 is formed such that the individual layerssubstantially alternate between first and second polymers. In somecases, by alternating polymer layers, e.g., especially between high andlow index polymer layers, a film may exhibit one or more desirableoptical properties. While the thirteen individual polymeric layersformed by first packet creator 56 alternate in an AB/AB pattern,embodiments are not limited as such. For example, in some embodiments,first packet creator 56 may be configured according to other patternssuch as A/B/B/A, A/A/A/BBB, A/BBB/A, and the like. In cases in whichadjacent slots in slot die section 68 a are fed similar materials, thismay result in a single polymeric layer rather than two individuallayers, which may have greater thickness than a polymeric layer formedvia only a single slot fed by a single conduit. Accordingly, the primarypacket created by first packet creator 56 is not limited to generating aprimary packet having thirteen alternating polymeric layers. In thismanner, first packet creator 56 provides for great flexibility inproperties and composition of the corresponding primary packet that itcreates. Moreover, as first and/or second packet creator 56 and 58 maybe configured to generate primary packets having more than two types ofpolymer layers, patterns other than described above are contemplated.For example, in the case of a primary packet having three differenttypes of polymeric layers, first and/or second packet creator 56 and 58may be configured to generate a primary packet having the pattern A/B/Cor A/C/B, as well as any other possible combinations of the threedifferent types of polymeric layers.

Upon exiting slot die section 68 a, the multilayer polymeric streamcorresponding to the first primary packet may be fed into compressionsection 74 a where the layers of the primary packet are compressed inthe transverse direction (y-direction) to decrease the thickness of theprimary packet. After being compressed in the compression section 74 a,the primary packet generated by first packet creator 56 is fed to packetcombiner 54, which combines the primary packet generated by first packetcreator 56 with the primary packet generated by second packet creator58.

As previously described, second packet creator 58 includes first flowchannel 60 b, second flow channel 62 b, first plurality of conduits 64b, second plurality of conduits 66 b (not shown in FIG. 2A), slot diesection 68 b, thermal tuning mechanisms 70 b and 72 b, and compressionsection 74 b. Each of these features may be configured substantially thesame or similar to that described with respect to the similarly numberedand named feature of first packet creator 56. Accordingly, second packetcreator 58 may be configured to generate a primary packet according tosubstantially the same or similar process described with respect to thegeneration of a primary packet by first packet creator 56. Once themultilayer polymeric stream corresponding to the primary packetgenerated by second packet creator 58 is compressed in compressionsection 74 b, the primary packet is fed to packet combiner 54 along withthat of the primary packet from first packet creator 56.

Packet combiner 54 includes first channel 76 a and second channel 76 bdefined by packet combiner housing 78. First channel 76 a is in fluidcommunication with compression section 74 a and may receive themultilayer polymeric stream corresponding to the primary packet generateby first packet creator 56 via inlet 80 a. Similarly, second channel 76b is in fluid communication with compression section 74 b and mayreceive the multilayer polymeric stream corresponding to the primarypacket generated by second packet creator 58 via inlet 80 b.

Packet combiner 54 may be configured to combine the first primary packetand the second primary packet with one another to form a singlemultilayer stream, generally represented in FIGS. 2A and 2B by numeral82. For example, as shown in FIGS. 2A and 2B, first channel 76 a andsecond channel 76 b may be configured relative to one another such thatthe multilayer flow streams corresponding to primary packets receivedvia inlets 80 a and 80 b, respectively, are reoriented within packetcombiner 54 from the original relative position that the primary packetswere received by packet combiner 54 and then combined into a singlemultilayer flow stream 82. In particular, first and second channels 76 aand 76 b may reorient the respective primary packets such that at leasta portion of the packets are stacked relative to one another when therespective packets are combined. For example, when the respectiveprimary packets have been reoriented to be suitably stacked, outermostsurfaces of the packets may be brought into contact with one another tocombine the respective primary packets into a single flow multilayerflow stream 82 via melt lamination.

In this manner, by combining the primary packets as described,multilayer flow stream 82 may include at least a portion of the primarypacket generated by first packet creator 56 and at least a portion ofthe second packet generated by second packet creator 58 in a stackedconfiguration. Accordingly, the number of individual layers possessed byat least a portion of multilayer flow stream 82 is approximately equalto that of the sum of the number of individual polymeric layers in therespective primary packets generated by first and second packet creators56 and 58. For example, multilayer flow stream 82 may include a total oftwenty-six individual layers in the example of FIGS. 2A and 2B, assumingthat the primary packet generated by first packet creator 56 and theprimary packet generated by second packet creator 58 each have a totalof thirteen individual polymeric layers. However, in some cases, if theouter layers of each respective primary packet that are brought intocontact with one another when the primary packets are combined areformed of substantially the same polymeric material, the two outerlayers may combine together to effectively form a single polymeric layerin the multilayer flow stream 82. In such cases, multilayer flow stream82 may include a total of twenty-five individual layers. The totalnumber of layers in such cases may generally be described by the formulax+y−1, where x equals the number of layers in the primary packetgenerated by the first packet creator and y equals the number of layersin the primary packet generated by the second packet creator.

In some embodiments, the flow geometry of one or more portions of packetcombiner 54, e.g., channels 76 a and 76 b, may be designed to achieveuniform spreading of the respective primary packets in the cross-webdirection (x-direction), in addition to reorienting the respectivepackets such that at least a portion of the primary packets are stackedwhen combined with one another. For example, first channel 76 a and/orsecond channel 76 b may be designed to spread a received primary packetin the cross-web direction. As will be described further below, in someexamples, first channel 76 a and second channel 76 b may be configuredto spread the respective packets in the cross-web direction prior tocombining the flow streams of the respective packets to form multilayerflow stream 82.

Still referring to FIGS. 2A and 2B, the multilayer flow stream 82resulting from the combination of the received primary packets exitspacket combiner 54 via outlet 84. Depending on the number of individuallayers desired for the manufactured multilayer polymeric film,multilayer flow stream 82 may or may not undergo further processing toincrease the number of layers of flow stream 82 before being processedvia an extrusion die. For example, if the number of polymeric layers inmultilayer flow stream 82, i.e., a number substantially equal to that ofthe sum of the layers in the first and second primary packets, issuitable for the desired multilayer film, then multilayer flow stream 82may be fed to an extrusion die without layer multiplication by amultiplier device. To the extent required, flow stream 82 may be spreadin the cross-web direction by a spreading manifold within the extrusiondie. In some example, the primary packet generated by first and secondpacket creators 56, 58 may be separately fed into an extrusion die andthen spread in the cross-web direction via spreading manifold prior tobeing combined with one another to form multilayer stream 82.

Alternatively, in some embodiments, multilayer flow stream 82 may beprocessed by a multiplier to increase the number of layers in thepolymeric flow stream that is processed by an extrusion die, e.g., ifthe number of layers in multilayer flow stream 82 is less than thelayers desired for the multilayer film being manufactured. However, forat least the reasons previously identified with respect to layermultiplication by a multiplier device, in some embodiments, it may bedesirable to configure first and second packet creators 56 and 58 suchthat the number of layers in resulting multilayer flow stream 82provides for a suitable number of layers without further layermultiplication. In such cases, one or more of the problems associatedwith the use of a multiplier device previously identified may beavoided.

While the embodiment of FIGS. 2A and 2B illustrates first and secondpacket creators 56 and 58 as being configured to generate primarypackets having thirteen individual polymeric layers, embodiments are notlimited to such a configuration. Instead, in some embodiments, a packetcreator may be configured to generate a primary packet including more orless than thirteen individual polymeric layers. For example, in someembodiments, packet creator 56 and/or 58 may be configured to generate aprimary packet having at least four individual polymeric layers. In someembodiments, first packet creator 56 and/or second packet creator 58 maybe configured such that the number of individual polymeric layers in theprimary packet generated by the respective packet creator may be atleast 4 individual layers, such as, e.g., at least 20 individual layers,at least 50 individual layers, at least 125 individual layers, or atleast 300 individual layers. In some examples, first packet creator 56and/or second packet creator 58 may be configured such that the numberof individual polymeric layers in the primary packet generated by therespective packet creator ranges from approximately 50 polymeric layersto approximately 1000 polymeric layers, such as, for example,approximately 100 polymeric layers to approximately 500 polymericlayers. In some examples, first and second packet creators 56 and 58 maybe configured to generated primary packets having substantially the samenumber of individual polymeric layers. In other examples, the number ofindividual layers in the primary packets generated by first packetcreator 56 may be different than that of the number of individual layersin the primary packet generated by second packet creator 58. In anycase, such primary packets may be stacked and combined as described inthis disclosure, e.g., to create a multilayer flow stream that haslayers in a number approximately equal to the sum of the number oflayers of each primary packet. Feedblock 50 is not limited embodimentsincluding only two packet creator sections, but may include more thantwo packet creator sections, such as, e.g., three packet creators orfour packet creators, in some embodiments. Each of the individual packetcreators may generate a separate primary packet in accordance with thisdisclosure.

Substantially all design parameters of the flow defining sections infirst packet creators 56, e.g., flow channels 60 a and 62 a, conduits 64a and 66 a, and slot die section 68 a, may be independent from the flowdefining sections in second packet creator 58, e.g., flow channels 60 band 62 b, conduits 64 b and 66 b, and slot die section 68 b. Parameterssuch as slot gap height, slot length, conduit diameter, channel widthsused in first packet creator 56 may be selected without effecting theselection of similar parameters in second packet creator 58. This mayallow for significant flexibility in the design and/or machining of theflow defining sections of the respective packet creators in feedblock50.

Moreover, as shown in FIGS. 2A and 2B, in some embodiments, feedblock 50may be configured such that one or more properties of the primary packetgenerated by first packet creator 56 may be substantially independentfrom that of the primary packet generated by second packet creator 58,and vice versa. For example, feedblock 50 may be configured such thatthe number of polymeric layers in the primary packet generated by firstpacket creator 56 may be substantially independent from the number ofpolymeric layers in the primary packet generated by second packetcreator 58, and vice versa. As configured in FIGS. 2A and 2B, the numberof layers in the primary packet generated by first packet creator 56 maybe primarily dependent on the configuration of slot die section 68 a andnumber of individual conduits of plurality of first and second conduits64 a and 66 a feeding slot die section 68 a. Similarly, the number oflayers in the primary packet generated by second packet creator 58 maybe primarily dependent on the configuration of slot die section 68 b andnumber of individual conduits of plurality of first and second conduits64 b and 66 b feeding slot die section 68 b.

In each case, the number of individual layers possessed by the firstprimary packet and the number of individual layers possessed by thesecond primary packet is dependent primarily on components of therespective packet creator generating the primary packet, rather than oneor more aspects of the other packet creator in feedblock 50. As oneresult, feedblock 50 may allow for greater flexibility in the overallrange of individual layers possessed by multilayer stream 82 and,accordingly, the multilayer film manufactured from stream 82, since thenumber of layers in respective primary packets are substantiallyindependent of one another.

As another example, in some embodiments, the composition of thepolymeric layers of the primary packet generated by first packet creator56 and the composition of the polymeric layers of the primary packetgenerated second packet creator 58 may be independent of one another. Asshown in FIGS. 2A and 2B, first flow channel 60 b and second flowchannel 62 b of second packet creator 58 may be separate and distinctfrom that of first and second flow channels 60 a and 62 a of firstpacket creator 56. Accordingly, the polymeric materials fed into firstand second flow channels 60 b and 62 b may be different than that of thepolymeric material fed into first and second flow channels 60 a and 60b.

In this manner, the polymeric materials that make up the individuallayers of the primary packet generated by second packet creator 58 maybe independent from that of the polymeric materials that make up theindividual layers of the primary packet generated by first packetcreator 56. As a result, in some cases, feedblock 50 may be capable ofproducing a multilayer stream 82 that includes four individual layerseach with distinct compositions, e.g., when packet creator 56 generatesa primary packet from polymeric A and polymeric B, and packet creator 58generates a primary packet from polymeric C and polymeric D. Since eachof polymers A-D may possess unique properties, e.g., refractive indexvalues and/or potential for birefringence when stretched, feedblock 50may provide for a greater ability to tailor the properties possessed bythe manufactured multilayer film compared to that of a feedblockconfigured to generate a multilayer flow stream having only twodifferent polymeric layers. Although the individual polymeric layers ofprimary packets may be described herein as including only a singlepolymeric material, it is recognized that in some embodiments, theindividual polymeric layers may include a mixture of two or moresuitable materials, rather than only a single polymeric material.

As another example, in some embodiments, feedblock 50 may be configuredsuch that the layer thickness profiles of the primary packet generatedby first packet creator 56 and the primary packet generated by secondpacket creator 58 are substantially independent from one another. Asconfigured in FIGS. 2A and 2B, for example, the components of firstpacket creator 56 that influence the layer thickness profile of theprimary packet generated by first packet creator 56 (e.g., slot diesection 68 a, first and second plurality of conduits 64 a and 66 a, andfirst and second flow channels 60 a and 62 a) are substantially separateand distinct from that of the corresponding components of second packetcreator 58. Likewise, the components of second packet creator 58 thatinfluence the layer thickness profile of the primary packet generated bysecond packet creator 58 (e.g., slot die section 68 b, first and secondplurality of conduits 64 b and 66 b, and first and second flow channels60 b and 62 b) are substantially separate and distinct from that of thecorresponding components of first packet creator 56. As a result, firstpacket creator 56 and second packet creator 58 may be able to generateseparated primary packets having layer thickness profiles substantiallyindependent from one another.

Furthermore, not only may the layer thickness profiles of the respectiveprimary packets generated by packet creators 56 and 58 be independent ofone another, the layer thickness profiles of the respective primarypackets may also be controlled or “tuned” independently of one another.For example, in FIGS. 2A and 2B, tuning mechanisms 70 a and 72 a offirst packet creator 56 are substantially separate from that of tuningmechanisms 70 b and 72 b of second packet creator 58. As previouslydescribed, tuning mechanisms 70 a and 72 a may selectively provide heatto the polymeric materials flowing in plurality of conduits 64 a and 66a, and tuning mechanisms 70 b and 72 b may selectively provide heat tothe polymeric materials flowing in plurality of conduits 64 b and 66 b.In such a configuration, tuning mechanisms 70 a and 72 a may selectivelyprovide heat to control or “tune” the layer thickness profile of theprimary packet generated by first packet creator 56 as described withoutsubstantially influencing the layer thickness profile of the primarypacket generated by second packet creator 58, e.g., by minimizing orpreventing “cross-talk” between the packets when tuning is required, andvice versa.

In some embodiments, first packet creator 56 and second packet creator58 may be substantially thermally isolated from one another. Asillustrated in FIG. 2A, feedblock 50 may include isolation section 86provided between first packet creator housing 57 and second packetcreator housing 59. Isolation section 86 may provide substantial thermalisolation between first and second packet creators 56 and 58. In someembodiments, isolation section 86 may simply be a physical void spacebetween first packet creator housing 57 and second packet creatorhousing 59. However, in other embodiments, isolation section 86 mayinclude one or more materials that provide appropriate thermal isolationbetween first and second packet creators 56 and 58, as described. In anycase, the composition (or lack of in embodiments in which section 86 isa physical void space) and/or the relative dimensions of isolationsection 86 may be designed to provide the appropriate amount of thermalisolation between first and second packet creators 56 and 58 such thatthe layer thickness profiles of the primary packets generated by therespective packets creators may be control or “tuned” substantiallyindependently of one another due at least in part to the relativethermal isolation provided by isolation section 86. Furthermore, usingseparate packet creators, the temperatures of the input polymers foreach primary packet generated in feedblock 50 may differ between therespective packet creators. Similarly, the temperatures of each packetcreator and the flow within the packet creators may be different betweenthe respective packet creators.

As configured, the ratio of thicknesses between the primary packetgenerated by first packet creator 56 and the primary packet generated bysecond packet creator 58, i.e., the multiplication ratio, may bedetermined by the mass flow rate of material supplied to each respectivepacket creator, e.g., rather than by the flow resistance of the channelgeometry of a layer multiplier device, as previously described. As aresult, the multiplication ratio can be directly adjusted during a runto compensate for material property variations or deviations of processconditions from assumptions made during the original design.

FIG. 3A is an example cross-sectional view illustrating feedblock 50along line A-A in FIG. 2A. In particular, FIG. 3A illustrates slot diesections 68 a and 68 b of feedblock 50, which are separated by isolationsection 86. As previously described, isolation section 86 may providesubstantial thermal isolation between first and second packet creators56 and 58.

As shown, slot die sections 68 a and 68 b each include a plurality ofslots 90 a and 90 b, respectively, which correspond to the plurality ofindividual polymeric layers in the primary packet generated by thecorresponding packet creator. The layer thickness profile of the primarypacket generated by first packet creator 56 may depend on the relativegeometry of plurality of slots 90 a within slot die section 68 a.Likewise, the layer thickness profile of the primary packet generated bysecond packet creator 58 may depend on the relative geometry ofplurality of slots 90 b within slot die section 68 b. As previouslydescribed, physically separating slot die sections 68 a and 68 b mayassist in providing substantial thermal isolation between first andsecond packet creators 56 and 58, allowing for independent control or“tuning” of each individual primary packet, as previously described.

FIGS. 3B and 3C illustrate alternate example cross-sectional viewsillustrating feedblock 50 along A-A. The examples shown in FIGS. 3B and3C are substantially similar to that shown in FIG. 3A. However, in FIG.3A, plurality of slots 90 a within slot die section 68 a are aligned inthe transverse direction (y-direction) with plurality of slots 90 bwithin slot die section 68 a. In FIG. 3B, plurality of slot 90 a withinslot die section 68 a are aligned in the transverse direction(y-direction) with plurality of slots 90 b within slot die section 68 abut are offset relative to one another in the y-direction. In such aconfiguration, each individual slot within slot die sections 68 a and 68b has a slot directly across from the respective slot in the adjacentslot die section except for the top slot of plurality of slots 90 a andthe bottom slot of plurality of slots 90 b. In FIG. 3C, plurality ofslots 90 a and plurality of slots 90 b are offset from one another byapproximately half of that shown in FIG. 3B. If such a configuration,the plurality of slots 90 a are in essence interleaved with plurality ofslots 90 b rather than being aligned with each other in the transverse(y-direction). As illustrated by FIGS. 3A-3C, slot die sections 68 a and68 b may or may not be oriented such that plurality of slots 90 a and 90b are offset from one another, and may be aligned with one another ormay be interleaved with one another in the y-direction.

FIGS. 4A and 4B are conceptual diagrams illustrating example feedblock150. Similar to feedblock 50 of FIGS. 2A and 2B, feedblock 150 may beused in a film line configured to manufacture multilayer polymericfilms, such as film line 10 of FIG. 1. In some aspects, feedblock 150may be configured the same or similar to that of feedblock 50, and mayinclude one or more feature which are substantially similar to featurespreviously described with respect to feedblock 50 of FIGS. 2A and 2B.Accordingly, similar features of feedblock 150 are labeled similarly tothose of feedblock 50. For example, feedblock 150 includes first andsecond flow channels 160 a and 162 a, respectively, which aresubstantially the same or similar to first and second flow channels 60 aand 62 a, respectively, of feedblock 50.

As shown in FIGS. 4A and 4B, feedblock 150 includes packet creatorsection 152 and packet combiner 154, which act in combination togenerate the described multilayer flow stream output from the receivedpolymeric materials. Packet creator section 152 includes first packetcreator 156 within housing 157, and second packet creator 158 withinhousing 159.

First packet creator 156 includes first flow channel 160 a, second flowchannel 162 a, first plurality of conduits 164 a, second plurality ofconduits 166 a (not shown in FIG. 4A), slot die section 168 a, thermaltuning mechanisms 170 a and 172 a, and compression section 174 a.Similarly, second packet creator 158 includes first flow channel 160 b,second flow channel 162 b, first plurality of conduits 164 b, secondplurality of conduits 166 b (not shown in FIG. 4A), slot die section 168b, layer thickness tuning mechanisms 170 b and 172 b, and compressionsection 174 b.

First packet creator 156 and second packet creator 158 are eachconfigured to independently generate a single primary packet. Afterfirst packet creator 156 and second packet creator 158 generate theirrespective individual primary packets, packet combiner 154 receives theprimary packets via inlets 180 a and 180 b of first and second channel176 a and 176 b, respectively, and combines them into a singlemultilayer flow stream 182.

Feedblock 150 may differ from feedblock 50 in FIGS. 2A and 2B in one ormore aspects. For example, as illustrated in FIGS. 4A and 4B, packetcreator section 152 of feedblock 150 may be configured differently thanthat of packet creator section 52 of feedblock 50. In particular, theconfiguration of first packet creator housing 157 and second packetcreator housing 159 allows for first packet creator 156 and secondpacket creator 158 to be placed in relatively closer proximity than thatof first packet creator 56 and second packet creator 58 of feedblock 50.Additionally, feedblock 150 may not include an isolation section alongthe boundary between first and second packet creators 156 and 158.

By placing first and second packet creators 156 and 158 in closeproximity to each other relative to the x-direction, the relative amountof cross-web direction change (x-direction) required to stack andcombine the primary packets generated by first and second packetcreators 156 and 158, respectively, is reduced compared to that requiredin feedblock 50. It is believed that such a configuration may reducecross-web layer non-uniformities in the respective primary packets andmultilayer flow stream 182.

FIGS. 5A-5C are conceptual diagrams illustrating another examplefeedblock 250. Similar to feedblock 50 of FIGS. 2A and 2B, feedblock 250may be used in a film line configured to manufacture multilayerpolymeric films, such as film line 10 of FIG. 1. In some aspects,feedblock 250 may be configured the same or similar to that of feedblock50, and may include one or more features which are substantially similarto features previously described with respect to feedblock 50 of FIGS.2A and 2B. Accordingly, similar features of feedblock 250 are labeledsimilarly to those of feedblock 50. For example, feedblock 250 includesfirst and second flow channels 260 a and 262 a, respectively, which aresubstantially the same or similar to first and second flow channels 60 aand 62 a, respectively, of feedblock 50.

As shown in FIGS. 5A-5C, feedblock 250 includes packet creator section252 and packet combiner 254, which act in combination to generate thedescribed multilayer flow stream output from the received polymericmaterials. Packet creator section 252 includes first packet creator 256which is enclosed within housing 257, and second packet creator 258which is enclosed within housing 259.

First packet creator 256 includes first flow channel 260 a, second flowchannel 262 a, first plurality of conduits 264 a, second plurality ofconduits 266 a (not shown in FIG. 5A), slot die section 268 a, thermaltuning mechanisms 270 a and 272 a, and compression section 274 a.Similarly, second packet creator 258 includes first flow channel 260 b,second flow channel 262 b, first plurality of conduits 264 b, secondplurality of conduits 266 b (not shown in FIG. 5A), slot die section 268b, thermal tuning mechanisms 270 b and 272 b, and compression section274 b.

First packet creator 256 and second packet creator 258 are eachconfigured to independently generate a single primary packet. Afterfirst packet creator 256 and second packet creator 258 generate theirrespective individual primary packets, packet combiner 254 receives theprimary packets via inlets 280 a and 280 b of first and second channel276 a and 276 b, respectively, and combines them into a singlemultilayer flow stream 282.

Feedblock 250 may differ from feedblock 50 in FIGS. 2A and 2B in one ormore aspects. For example, as shown in FIGS. 5A-5C, first packet creatorsection 256 includes thermal tuning devices 292 a and 294 a proximate toslot die section 268 a. Likewise, second packet creator section 258includes thermal tuning devices 292 b and 294 b proximate to slot diesection 268 b. In some embodiments, tuning devices 292 a and 294 a mayselectively provide heat to all or portions of slot die section 268 a.Similarly, tuning devices 292 b and 294 b may selectively provide heatto all or portions of slot die section 268 b. In each case, the heatprovided to slot die sections via the tuning devices may act to controlor “tune” one or more properties of the primary packet created by thecorresponding packet creator, such as, e.g., the cross-web layerthickness profile of a primary packet. Tuning devices 292 a, 292 b, 294a, and/or 294 b may be used in addition to, or instead, of tuningdevices 270 a, 270 b, 272 a, and/or 272 b as previously described.

As shown in FIG. 5A, first packet creator housing 257 and second packetcreator housing 259 are separated by isolation section 286, which mayprovide substantial thermal isolation between first and second packetcreators 256 and 258. In some embodiments, isolation section 286 maysimply be a physical void space between first packet creator housing 257and second packet creator housing 259. However, in other embodiments,isolation section 286 may include one or more materials that provideappropriate thermal isolation between first and second packet creators256 and 258, as described. In any case, the composition (or lack of inembodiments in which section 286 is a physical void space) and/or therelative dimensions of isolation section 286 may be designed to providethe appropriate amount of thermal isolation between first and secondpacket creators 256 and 258 such that the layer thickness profiles ofthe primary packets generated by the respective packets creators may becontrol or “tuned” substantially independently of one another due atleast in part to the relative thermal isolation provided by isolationsection 286.

As another example difference from feedblock 50, first and second packetcreators 256 and 258 are configured such that the primary packets areformed substantially along flow directions (represented approximately bylines 296 a and 296 b in FIG. 5A) that are non-parallel to the flowdirection at which packet combiner 254 combines the generated primarypackets into a single multilayer flow stream 282, as previouslydescribed, rather than forming the primary packets along flow directionsthat are substantially parallel to the flow direction at which packetcombiner 54 combines the generated packets in feedblock 50.

As shown, the relative flow direction 296 a in which first packetcreator 256 generates the first primary packet forms angle 298 a withlongitudinal axis 300 along which packet combiner 254 combines therespective primary packets to form multilayer flow stream 282.Similarly, the relative flow direction 296 b in which first packetcreator 258 generates the second primary packet forms angle 298 b withlongitudinal axis 300 along which packet combiner 254 combines therespective primary packets to form multilayer flow stream 282.

By configuring feedblock 250 such that angles 296 a and/or 296 b aregreater than zero, i.e., non-parallel with flow direction 300,sufficient thermal isolation between packet creators 256 and 258, e.g.,via isolation section 286, may be provided to allow for substantiallyindependent control or “tuning” of the respective primary packets, whilealso minimizing the relative degree of realignment of the respectiveprimary packet flows in the x-direction that is required within packetcombiner 254. In some embodiments, angles 296 a and/or 296 b may begreater than zero degrees to less than 90 degrees. In some embodiments,angles 296 a and/or 296 b may range from approximately 5 degrees toapproximately 60 degrees, such as, e.g., approximately 5 degrees toapproximately 30 degrees. In some embodiments, angle 296 a may beapproximately equal to that of angle 296 b, while in other embodimentsangle 296 a may be different than that of angle 296 b.

Referring to FIG. 5C, packet combiners 274 a and 274 b may function toredirect the flow of the respective primary packets from slot diesections 268 a and 268 b, respectively, to compress the thickness of aprimary packet (in the y-direction) while substantially maintaining theuniformity of the width of layers in the cross-web direction(x-direction). Compression section 274 a compresses the primary packetflow in first packet creator 256 to first centerline 296 a, andcompression section 274 b compresses the primary packet flow in secondpacket creator 258 to second centerline 296 b. As shown, in someembodiments, first centerline 296 a and second centerline 296 b may beoffset from one another relative to the y-direction. In this manner,feedblock 50 may minimize distortions that can result from reorientationof the primary packets within packet combiner 254, as previouslydescribed.

FIGS. 6A-6K are conceptual diagrams illustrating example feedblocks 350a-350 k, respectively, which are each designed to generate two primarypackets via two separate packet creators. FIG. 6L is a conceptualdiagram illustrating example feedblock 350 k from a side view.

Similar to feedblock 50 (FIGS. 2A and 2B), feedblock 150 (FIGS. 4A and4B), and feedblock 250 (FIGS. 5A-5C), each of feedblocks 350 a-350 k maybe used in a film line configured to manufacture multilayer polymericfilms, such as film line 10 of FIG. 1. In some aspects, feedblocks 350a-350 k may be configured the same or substantially similar to that offeedblocks 50, 150, and/or 250, and may include one or more featureswhich are substantially similar to features previously described withrespect to feedblocks 50, 150, and/or 250. For ease of description,similar features of feedblocks 350 a-350 k are generally named andnumbered similarly to those of feedblock 50. For example, feedblocks 350a-350 k includes first and second flow channels 360 a and 362 a,respectively, which may be substantially the same or similar to firstand second flow channels 60 a and 62 a, respectively, of feedblock 50.

Also for ease of description, like features of each of feedblocks 350a-350 k are similarly named and numbered throughout FIGS. 6A-6K whereapplicable. For example, each of feedblocks 350 a-350 k includes firstpacket creator 356 and second packet creator 358. However, similarnaming and numbering of features between feedblocks 350 a-350 k does notnecessarily imply identical configuration between the various featurespossessed by feedblocks 350 a-350 k. Rather, as will be apparent fromthe following description of feedblocks 350 a-350 k, various designdifferences exist between feedblock 350 a-350 k, which may influence theoperation of each of feedblock 350 a-350 k compared to one another.

As shown in FIGS. 6A-6K, each of feedblocks 350 a-350 k includes firstpacket creator 356 and second packet creator 358. First packet creator356 and second packet creator 358 are each configured to generate asingle primary packet in a manner substantially independently from oneanother. Unless otherwise noted, first packet creator 356 includes firstflow channel 360 a, second flow channel 362 a, first plurality ofconduits 364 a, second plurality of conduits 366 a (not shown), slot diesection 368 a, thermal tuning mechanisms 370 a and 372 a, andcompression section 374 a. Similarly, second packet creator 358 includesfirst flow channel 360 b, second flow channel 362 b, first plurality ofconduits 364 b, second plurality of conduits 366 b (not shown), slot diesection 368 b, thermal tuning mechanisms 370 b and 372 b, andcompression section 374 b.

For ease of illustration, first and second packet creators 356 and 358of feedblock 350 j (FIG. 6J) and feedblock 350 k (FIG. 6L) areillustrated as generally including first and second layer generationelements 375 a and 375 b, respectively, in place of the features of flowchannels 360, 362, conduits 364, 366, and/or thermal tuning mechanisms370, 372. In general, first and second layer generation elements 375 aand 375 b of feedblocks 350 j and 350 k may feed slot die sections 368 aand 368 b, respectively, in a manner that allows for first and secondpacket creators 356 and 358 to independently generate primary packets incombination with compression sections 374 a and 374 b. As such, in someembodiments, first and second layer generation elements 375 a and 375 bmay include any suitable configuration of flow channels 360, 362,conduits 364, 366, and/or thermal tuning mechanisms 370, 372, includingone or more of the example configurations described in this disclosure.Additionally, feedblock 350 j includes third packet creator 361 forgenerating a third primary packet that is combined with the primarypackets generated by first and second packet creators 356, 358. Thirdpacket creator 361 includes third layer generation element 375 c andslot die section 368 c, and may be the same or substantially similar tothat of first and second packet creators 356, 358.

As one exception to the above description, as shown for feedblock 350 hin FIG. 6H, first packet creator 356 and second packet creator 358 eachinclude only a single thermal tuning mechanism (thermal tuning mechanism370 a and 370 b, respectively) adjacent to one side of first pluralityof conduits 364 a and second plurality of conduits 364 b, respectively.Similarly, first packet creator 356 and second packet creator 358 offeedblock 350 c in FIG. 6C each include only a single thermal tuningmechanism (thermal tuning mechanism 370 a and 370 b, respectively),which are shown located between first conduits 364 a and second conduits366 a (not shown) in first packet creator 356 and first conduits 364 band second conduits 366 b (not shown) in second packet creator 358.However, in other examples, first packet creator 356 and/or secondpacket creator 358 of feedblock 350 h and feedblock 350 c may includetwo or more thermal tuning mechanisms. In such examples, the thermaltuning mechanisms may be located adjacent to both sides of firstconduits 364 a and second conduits 364 b.

The components of first and second packet creators 356, 358 may functionto generate both primary packets in the same or substantially similarmanner to that described above with regard to feedblocks 50, 150, and250. After first packet creator 356 and second packet creator 358generate respective individual primary packets, the primary packets arecombined downstream at some point to form a single multilayer flowstream 382. In some embodiments, the first and second packets may becombined with one another without substantially spreading one or both ofthe packets in the cross-web (x-direction) prior to being combined toform multiplayer flow stream 382. Such a feature may be embodied, forexample, in feedblocks 350 a-f and 350 h-j as shown in FIGS. 6A-F and6H-J, respectively.

In other embodiments, one or more of the first and second primarypackets generated by first and second packet creators 356, 358,respectively, may be spread in the cross-web direction prior to thefirst and second packets being combined with one another. An example ofsuch an embodiment is shown in FIG. 6G, in which both the first andsecond packets generated by first and second packet creators 356, 358,respectively, are spread in the cross-web direction (x-direction) priorto being combined with one another to form multilayer stream 382.Examples of cases in which packets generated by first and second packetcreators 356, 358 are spread in the cross-web direction prior to beingcombined with one another are described further below, for example, withregard to FIGS. 10, 11, 13, and 15.

In some embodiments, a packet creator section of a feedblock may includeone or more inserts that define the plurality of conduits and slotswithin the packet creator, such as, e.g., first and second conduits 364a, 366 a and the slot portion of slot die section 368 a within firstpacket creator 356. In FIGS. 6A-K, for ease of description, such insertsmay be individually referred to as insert 390 a or 390 b, and generallyreferred to as insert 390.

Insert 390 may be one or more plates designed to be removably insertedinto a corresponding receiving portion defined by the housing of apacket creator section. In this manner, insert 390 may be removed formodification of conduits 364 a, 366 a and/or slot 368 a (e.g., viamachining) or replaced with another insert 390 designed to provide fordifferent flow through conduits 364 a, 366 a and/or slots 368 a. Assuch, insert 390 may provide more added flexibility for adjusting theflow characteristics defined by conduits 364 a and slots 368 a of firstpacket creator section 356.

In some embodiments, a common insert may be used to define both theconduits and slots for both a first and second packet creator section ofa feedblock. For example, as shown for feedblock 350 c of FIG. 6C, firstand second plurality of conduits 364 a, 366 a, and slots die section 368a of first packet creator section 356 are defined by first insert 390 awhich also defines first and second plurality of conduits 364 b, 366 b,and slot die section 368 b of second packet creator section 358. Similarfeedblock examples are shown in FIGS. 6D, 6E, 6H, and 6I.

Alternatively, separate inserts may be used to define the conduits andslots for two packet creator sections of a feedblock. For example, asshown for feedblock 350 a of FIG. 6A, first packet creator section 356includes first insert 390 a that defines first and second conduits 364a, 366 a, and slot die section 368 a, and second packet creator section358 include first insert 390 b that defines first and second conduits364 b, 366 b, and slot die section 368 b. Insert 390 a may be removed,replaced and/or modified independent of insert 390 b, and vice versa.Similar examples are shown in FIGS. 6B, 6F, 6Q 6J, and 6K.

In addition to the option of having the conduits and slots of multiplepacket creators either defined by a common insert or separate inserts,the conduits and slots of a packet creator section may be defined byseparate inserts or common inserts. For example, a single insert maydefine first and second conduits 364 a, 366 a and slot die section 368 aof first packet creator section 356. Or, alternatively, first and secondconduits 364 a, 366 a may be defined by a separate insert from that ofslot die section 368 a. Such an example is shown in FIG. 6B, in whichfirst insert 390 a defines first and second conduits 364 a, 366 a,second insert 390 b defines first and second conduits 364 a, 366 a,third insert 390 c defines slots die section 368 a, and fourth insert390 d defines slot die section 368 b. In cases in which separate insertsmay be used for defining conduits 364 a, 366 a and slot die section 368a, those inserts may be common or separate from that of the one or moreinserts used to define conduits 364 b, 366 b, and/or slot die section368 b of second packet creator 358.

In a similar fashion, in some embodiments, a packet creator section of afeedblock may include one or more gradient plate manifolds that definethe flow channels of the packet creator, such as, e.g., first and secondflow channels 360 a, 362 a within first packet creator 356. In FIGS.6A-K, for ease of description such gradient plate manifolds may beindividually referred to as gradient plate manifolds 392 a or 392 b, andgenerally referred to as gradient plate manifolds 392. Gradient platemanifold 392 may be removable from the housing of a packet creatorsection. In this manner, gradient plate manifold 392 may be removed formodification of, for example, flow channels 360 a, 362 a or replacementwith another gradient plate manifold 392 designed to provide fordifferent flow through flow channels 360 a, 362 a. As such, gradientplate manifold 392 may provide more added flexibility for adjusting theflow characteristics defined by first and second flow channels 360 a,362 a of first packet creator section 356.

In some example, a common gradient plate manifold may be used to defineboth the first and second flow channels of first and second packetcreator section of a feedblock. For example, as shown for feedblock 350c of FIG. 6C, first and second channels 360 a, 362 a of first packetcreator section 356 are defined by first gradient plate 392 a which alsodefines first and second channels 360 b, 362 b of second packet creatorsection 358. Similar feedblock examples are shown in FIGS. 6D and 6E.

Alternatively, separate gradient plate manifolds may be used to definethe flow channels for two packet creator sections of a feedblock. Forexample, as shown for feedblock 350 a of FIG. 6A, first packet creatorsection 356 includes first gradient plate manifold 392 a that definesfirst and second flow channels 360 a, 362 a, and second packet creatorsection 358 include first gradient plate manifold 392 b that definesfirst and second flow channels 360 b, 362 b of second packet creator358. Similar examples are shown in FIGS. 6B, 6F, 6Q 6H, 6I, 6J, and 6K.

The location of the flow channels defined by a gradient plate manifoldmay vary with respect to the conduits fed by the flow through the flowchannels. For example, in feedblock 350 a of FIG. 6A, first and secondflow channels 360 a, 362 a defined by gradient plate manifold 392 a offirst packet generator 356 are configured to feed first and secondconduits 364 a, 366 a from a position above conduits 364 a, 366 a, withrespect to the flow direction of the primary packets generated by thefirst and second packet creators 356, 358. A similar configuration isexhibited by second packet creator 358 of feedblock 350 a. First andsecond packet creators 356, 358 of feedblocks 350 b, 350 c, 350 d, 350f, 350 g, and 350 k also exhibit a similar design configuration.

As an alternative design, in feedblock 350 h (FIG. 6H), first and secondflow channels 360 a, 362 a defined by gradient plate manifold 392 a offirst packet generator 356 are configured to feed first and secondconduits 364 a, 366 a from a position beside conduits 364 a, 366 a withrespect to the flow direction of the primary packets generated by thefirst and second packet creators 356, 358. A similar configuration isexhibited by second packet creator 358 of feedblock 350 h. Feedblock 350i also exhibits a similar design configuration.

As another alternative design, in feedblock 350 e (FIG. 6E), first andsecond flow channels 360 a, 362 a defined by gradient plate manifold 392a of first packet generator 356 are configured to feed first and secondconduits 364 a, 366 a from a position below conduits 364 a, 366 a withrespect to the flow direction of the primary packets generated by thefirst and second packet creators 356, 358. A similar configuration isexhibited by second packet creator 358 of feedblock 350 e.

First and second conduits 364 a, 366 a defines the flow direction ofpolymeric melt streams from first and second flow channels 360 a, 362 aas delivered to slot die section 368 a in first packet section 356. Insome embodiments, first and second conduits 364 a, 366 a are configuredsuch that the flow within the conduits is substantially parallel to thatof the flow within slot die 368 a and/or compression section 374 a whendelivered to slot die section 368 a. Such an example configuration isexhibited by both first and second packet creator 356, 358 of feedblocks350 a, 350 b, 350 d, 350 f, 350 g, 350 i, and 350 k.

In other embodiments, first and second conduits 364 a, 366 a areconfigured such that the flow within the conduits 364 a, 366 a whendelivered to slot die section 368 a is substantially non-parallel tothat of the flow within slot die 368 a and/or compression section 374 a.Such an example configuration is exhibited by first and second packetcreators 356, 358 of feedblock 350 e (where the flow direction issubstantially orthogonal to flow within slot die section 368 a, 368 bwhen delivered to slot die section 368 a, 368 b) and feedblocks 350 cand 350 h (where the flow direction is substantially diagonal to flowwithin slot die section 368 a, 368 b when delivered to slot die section368 a, 368 b).

Slot die section 368 a may have a center feed design in which flow fromfirst and second conduits 364 a, 366 a enter slot die section 368 a atapproximately the center of slot die section 368 a in the cross-web(x-direction). Such a configuration is exhibited by first and secondpacket creators 356, 358 of feedblocks 350 a, 350 b, 350 c, 350 f, 350g, 350 h, and 350 i.

In other embodiments, slot die section 368 a may have a non-center feeddesign in which flow from first and second conduits 364 a, 366 a enterslot die section 368 a at a position other than that of approximatelythe center of slot die section 368 a in the cross-web (x-direction). Forexample, slot die section 368 a may have a side feed design in whichflow from the first and second conduits 364 a, 366 a enter slot diesection 368 a at a side or edge of slot die section 368 a in thecross-web (x-direction). Such a configuration is exhibited by first andsecond packet creators 356, 358 of feedblocks 350 d and 350 e.

The position of one or more thermal tuning mechanisms with regard to theconduits of a packet creator section may vary. For example, within firstpacket creator 356 of feedblock 350 a (FIG. 6A), thermal tuningmechanisms 370 a, 372 a are positioned symmetrically on either side offirst and second conduits 364 a, 366 a. A similar configuration isexhibited by second packet creator 358 of feedblock 350 a. Feedblocks350 b, 350 d-350 g, 350 i and 350 k also exhibit a similar designconfiguration. Feedblocks 350 c (FIG. 6C) and 350 h (FIG. 6H) exhibit analternate design in which first and second packet creators 356, 358include only a single thermal tuning mechanism 370 a, 370 b,respectively, which is located adjacent to one side of first and secondflow conduits 364 a, 364 b, 366 a, 366 b.

The flow direction of the multiple layers within the compressionsections of respective packet creator sections may be parallel ornon-parallel to one another. For example, in feedblock 350 a, the flowwithin compression section 374 a of first packet creator 356 issubstantially parallel to the flow within compression section 374 b ofsecond packet creator 358. First and second compression sections 374 a,374 b of feedblocks 350 b, 350 c, 350 d, 350 e, 350 g, 350 h, 350 i,and, 350 k exhibit the same or substantially similar configuration. Infeedblock 350 j (FIG. 6J), the flow within first and second compressionsections 374 a, 374 b is substantially parallel but opposite to oneanother. In each of feedblocks 350 j and 350 k, the first and secondcompression sections 374 a, 374 b are stacked on one another in they-direction rather than being positioned side-by-side. In feedblock 350f (FIG. 6F), the flow within first and second compression sections 374a, 374 b is non-parallel to one another and both define a flow directionthat is non-parallel to the flow of multilayer flow stream 382, which isthe combination of first and second primary packets generated by firstand second packet creators 356, 358. Furthermore, feedblock 350 jincludes third packet creator 361 for generating a third primary packetalong a flow direction that is substantially orthogonal to the flowwithin both the first and second compression sections 374 a, 374 b.

In embodiments in which the first and second compression sections 374 a,374 b of first and second packet creators 356, 358, respectively, areparallel to one another, for example, the relative distance between eachcompression section 374 a, 374 b (as well as slot die sections, 368 a,368 b) in the cross-web direction (x-direction) may be a designconsideration. For example, distance between first and secondcompression sections 374 a, 374 b may determine the relative degree thatthe flows of the first and second primary packets generated by first andsecond packet creators 356, 358 must be redirected in the cross-webdirection (x-direction) to be combined with one another in stackedconfiguration, e.g., within a packet combiner section, to formmultilayer flow 382. First and second compression sections 374 a, 374 bof feedblock 350 e and 350 d are relatively closer together in thecross-web direction compared to that of feedblock 350 a, for example.Such a configuration may be enabled by the side feed design of slot diesections 368 a, 368 b of feedblocks 350 d, 350 e, as described above.The design of feedblocks 350 j and 350 k allows first and secondcompression sections 374 a, 374 b of first and second packet creators356, 358, respectively, to be aligned or stacked with one another in thecross-web direction. In such examples, the flows of the first and secondflows do not have to be significantly redirected in the cross-webdirection prior to being combined with one another, e.g., in a packetcombiner section, to form multilayer flow 382 in a stackedconfiguration.

In some embodiments, the relative location at which the first and secondpacket creators generate first and second primary packets, respectively,may be substantially the same as one another or staggered with oneanother relative the flow stream direction (e.g., z-direction). Forexample, for feedblock 350 a (FIG. 6A), first packet creator 356 isconfigured to generate the first primary packet at substantially thesame position as that at which second packet creator 358 generates thesecond packet relative to the flow stream direction. In such an example,the distance that each primary packet travels after being generated byfirst and second packet creators 356, 358 before being combined with oneanother to form multilayer flow stream 382 is substantially equal.Conversely, first and second packet creator sections of a feedblock maybe staggered with one another such that the distance that the firstprimary packet travels to combine with the second packet is greater thanthe distance that the second primary packet travels to combine with thefirst primary packet. Such a configuration may be represented bymodifying feedblock 350 a (FIG. 6A) such that the components of firstpacket creator section 356 are located at a different position along thez-direction than that of the components of second packet creator section358.

The degree to which individual packet creators may be isolated from oneanother in a feedblock including multiple packet creators may vary basedon one or more design factors. As described above, the degree of thermalisolation between first and second packet creators of a feedblock mayinfluence the degree to which each primary packet may be “tuned” orcontrolled independently with regard to the generation of the primarypackets by first and second packet creators. For example, the flow ofpolymeric material through one or more portion(s) of a packet creator(e.g., first and second conduits 364 a and 366 a of first packet creator356) and, therefore, the layer thickness profile, may be controlled bycontrolling the temperature at one or more locations within a packetcombiner section. Accordingly, to at least some extent, as the degree ofthermal isolation between respective packet creator sections increases,so does the degree to which thermally dependent properties of primarypackets generated by respective packet creators may be controlledindependently of one another within multi-packet creator feedblock.

In some embodiments, thermal isolation between packet creator sectionsmay be increased by increasing the distance between the components(e.g., first and second conduits, slot die section, compression section,and/or thermal tuning mechanisms) of the first packet creator and thecomponents of the second packet creator. In particular, the degree ofthermal isolation between respective packet creator sections may dependon the physical distance separating the thermal tuning mechanisms of onepacket creator (e.g., thermal tuning mechanisms 370 a, 372 a of firstpacket creator 356) from that of the flow defining components of anotherpacket creator (e.g., first and second conduits 364 b, 366 b of secondpacket creator 358).

As such, the physical distance between components of the first andsecond packet creators in the cross-web direction (x-direction) may beincreased to increase thermal isolation between the packet creators. Insome examples, a feedblock may optionally incorporate a thermalisolation section between first and second packet creators to reduce thethermal crosstalk between the packet creators. For example, as describedabove, feedblock 50 may include isolation section 86 (FIG. 2A) andfeedblock 250 may include isolation section 286 (FIG. 5A) to increasethe level of thermal isolation between the first and second packetcreators. However, while increasing the distance between the componentsof first and second packet creators and/or including thermal isolationsection between packet creators of a feedblock may increase the level ofthermal isolation between first and second packet creators, suchseparation may also increase the degree to which flows of the primarypackets generated by the respective packet creators must be redirectedprior to being combined to form a multilayer flow. In some examples, asthe angle at which the flow of two packets must be redirected to becombined is increased, the more difficult it may be to achieve and/ormaintain cross-web layer uniformity.

Additionally or alternatively, the distance between first and secondpacket creators 356, 358 may be increased by staggering the componentsof the respective packet creators of the flow direction (z-direction),e.g., as described above, compared to that of a configuration in whichthe first and second packet creators 356, 358 generate the respectiveprimary packet at substantially the same position as one another in theflow direction. As such, a staggered packet creator configuration mayincrease the thermal isolation between the respective packet creators ofa feedblock.

The level of thermal isolation between first and second packet creatorsmay also depend on whether a feedblock design includes separate orcommon conduit/slot inserts and/or gradient plate manifolds for thedifferent packet creator sections. As described above, a feedblock, suchas, e.g., feedblock 350 a of FIG. 6A, may be designed such that firstand second conduits 364 a, 366 a and/or slot die section 368 a of firstpacket creator 356 are defined by insert 390 a that is separate fromthat of insert 390 b that defines first and second conduits 364 b, 366 band/or slot die section 368 b of second packet creator 358, while afeedblock, such as, feedblock 350 c of FIG. 6C may be designed such thatsubstantially the same components are defined by insert 390 a with iscommon to first and second packet creators 356, 358. In some examples, adesign in which separate inserts are utilized for the conduits and slotdie section of separate packet creator sections may allow for increasedthermal isolation between the respective packet creator sectionscompared to designs in which a common insert is used to define theconduits and slot die section for the packet creator sections.Similarly, a design in which separate gradient plate manifolds areutilized for the first and second flow channels of separate packetcreator sections may allow for increased thermal isolation between therespective packet creator sections compared to designs in which a commongradient plate manifold is used to define the first and second flowchannels for the packet creator sections.

The example feedblock configurations described in this disclosure forgenerating multiple primary packets are primarily described forembodiments including substantially the same configuration for both thefirst and second packet creators. In such examples, the respectivepacket creators may be in essence mirror images of each other. However,other embodiments are contemplated for a feedblock including multiplepacket creators in which the respective packet creators are differentfrom one another. For example, in one embodiment for a feedblockincluding first and second packet creators for generating two primarypackets that are then combined with one another downstream, the firstpacket creator may be substantially the same as first packet creator 356of feedblock 350 a (FIG. 6A) and the second packet creator may besubstantially the same as second packet creator 358 of feedblock 350 c(FIG. 6C). In general, for example feedblocks including multipleindividual packet creators, the packet creators may be configuredsubstantially the same as any example packet creator described in thisdisclosure, and the multiple packet creators of an example feedblock mayhave substantially the same configurations as one another or may havedifferent configurations from one another.

As described above, in some embodiments, a multi-packet generatingfeedblock may be configured to generate multiple primary packets andthen combine the generated primary packets without substantiallyspreading the packets in the cross-web direction. For example, feedblock350 a illustrates a configuration in which the first and second primarypackets generated by first and second packet creators 356, 358 arecombined with one another in packet combiner section 354 to formmultilayer flow stream 382 without spreading either the first or secondprimary packet in the cross-web (x-direction).

Conversely, in some embodiments, a multi-packet generating feedblock maybe configured such that the primary packets generated by the respectivepacket creator sections are spread in the cross-web direction prior tobeing combined with one another to form a single multilayer flow stream.For example, feedblock 350 g of FIG. 6G illustrates a configuration inwhich the first and second primary packets generated by first and secondpacket creators 356, 358, respectively, are spread in the cross-webdirection prior to being combined with one another to form multilayerflow stream 382. In such a case, multilayer flow stream 382 has across-web width greater than that of the cross-web width of the firstand second primary packets as generated by first and second packetcreators 356, 358. As will be described further below, in some examples,the first and second primary packets may be individually spread in thecross-web direction via separate spreading manifolds of an extrusion die(not labeled in FIG. 6G).

As shown in FIG. 6G the alignment of the first and second primarypackets generated by first and second packet creators 356, 358,respectively, in the cross-web direction (x-direction) is such that thefirst and second packets are spread asymmetrically in the cross-webdirection prior to being combined. That is, each primary packet isspread further in one cross-web direction than the opposite cross-webdirection. In this manner, first and second primary packets aligned withone another in the cross-web direction prior to being combined. In otherexamples, the first and second primary packets may be realigned in thecross-web direction to be substantially aligned with one another andthen symmetrically spread in the cross-web direction prior to becombined with one another to form multilayer flow stream 382.Alternatively, first and second packet creators 356, 358 may be stackedwith one another rather than side-by-side (e.g., in manner the same orsimilar to that of feedblock 350 k of FIGS. 6K and 6L) such that thefirst and second primary packets are aligned with one another whengenerated by first and second packet creators 356, 358 without anysubstantial realignment in the cross-web direction. In such anembodiment, the first and second packets may be spread symmetrically inthe cross-web direction and then combined to form multilayer flow stream382 without realigning the respective packets in the cross-web directionprior to being combined with one another.

FIG. 7 is a conceptual diagram illustrating example multilayer flowstream 304. In particular, FIG. 7 represents multilayer flow stream 304within a packet combiner of a feedblock, and may illustrate examplecross-sectional views of packet combiner 54 of feedblock 50 along lineB-B shown in FIG. 2A. Such a cross-sectional view corresponds to a pointafter two primary packets have been combined with one another in astacked configuration in packet combiner 54. As such, flow stream 304includes first portion 306 corresponding to the primary packet generatedby a first packet creator, e.g., first packet creator 56, and secondportion 308 corresponding to the primary packet generated by a secondpacket creator, e.g., second packet creator 58.

As previously described, a packet combiner 36 may combine packets 38 and40 by reorienting the flow of the respective packets relative to oneanother other such that at least a portion of the respective primarypackets are stacked when combined by combiner 36. If at least a portionof packets 38 and 40 are stacked when combined with one another, then atleast a portion of the resulting multilayer stream 32 includes a totalnumber of individual layers approximately equal to that of the sum ofthe number of individual polymeric layers in packets 38 and 40.

Referring to FIG. 7, multilayer flow stream 304 is representative of anembodiment in which packet creator 54 has changed the orientation of afirst and second primary packet relative to one another such that firstportion 306 and second portion 308 are substantially fully stacked onone another when combined. In particular, the cross-web width(x-direction) of the first portion 306 and second portion 308 aresubstantially equal, and, as shown, the edges of portions 306 and 308are substantially aligned with one another in the cross-web direction.In this manner, substantially all of multilayer flow stream 304 includesa number of individual polymeric layers, along the y-direction, equal tothe sum of the number of layers in first portion 306 and second portion308. While FIG. 7 illustrates first portion 306 and second portion 308in a substantially fully stacked configuration, in some embodiments,packet combiner 54 may be designed such that first portion 306 andsecond portion 308 are only partially stacked on one another rather thansubstantially fully stacked on one another when combined. For example,the cross-web width (x-direction) of the first portion 306 and secondportion 308 may not be substantially equal to one another and/or theedges of portions 306 and 308 may not be substantially aligned with oneanother in the cross-web direction. In any case, the stackingconfiguration may allow for a multilayer flow stream including polymericlayers formed from both first packet creator 56 and second packetcreator 58 stacked on one another.

As shown in FIG. 7, first portion 306 and second portion 308 mayillustrate an example in which first and second multilayer packets arecombined to form multilayer flow stream 304 without being spread in thecross-web direction prior to being combined with one another. That is,the cross-web width of both first and second portions 306, 308 issubstantially that same as that of the cross-web width of primarypackets generated via first and second packet creators 56 and 58,respectively. In such an example, after the first and second packets arecombined to form multilayer flow stream 304, flow stream 304 may then bespread in the cross-web direction. For example, in some cases, withinextrusion die 20 (FIG. 1), multilayer flow stream 304 may enter aspreading manifold configured to spread the multilayer flow stream inthe cross-web direction prior to exiting extrusion die 20.

In other embodiments, such as those examples described below with regardto FIGS. 10, 11, 13, and 15, one or more primary packets or packetsderived there from (e.g., multilayer packets derived from a primarypacket via a multiplier device) may be spread in the cross-web directionprior to being combined with one another to form multilayer flow stream304. In some embodiments, flow stream 304 may be further spread in thecross-web direction after the individual packets are combined with oneanother after being spread individually in the cross-web direction.Alternatively, multilayer flow stream 304 may be formed by combiningmultilayer packets that have not been spread in the cross-web directionon an individual basis prior to being combined with one another to formmultilayer flow stream 304.

FIG. 8 is a conceptual diagram illustrating example packet combiner 401and extrusion die 403. Packet combiner 401 is configured such that oneor more supplemental layers may be added to first and second multilayerpackets 400 and 402, respectively, proximate to the multilayer packets400, 402 being combined with one another to form single multilayer flowstream 410. In particular, the various channels defined within packetcombiner 401 define the flow of first multilayer packet 400 (individuallayers not shown), second multilayer packet 402 (individual layers notshown), first skin layer 404, second skin layer 406, and core layer 408such that individual flows are combined with one another to formmultilayer flow stream 410. Such a configuration may be implemented, forexample, within any packet combiner section of a feedblock including butnot limited to one or more of the example feedblocks described herein,(e.g., packet combiner section 54 of feedblock 50). First multilayerpacket 400 and second multilayer packet 402 may be generated using anyfeedblock apparatus configuration described herein, although any othersuitable configuration capable of generating two or more multilayerprimary packets may also be used.

As shown in FIG. 8, prior to the combination of first packet 400 andsecond packet 402 within packet combiner 401, the flow path of corelayer 408 is directed between first packet 400 and second packet 402.Packet combiner 401 then directs the flows to combine core layer 408,first packet 400, and second packet 402 into a single flow, which issubsequently combined with the flows of skin layers 404 and 406 to formmultilayer flow 410. After multilayer flow 410 is generated by packetcombiner 401, multilayer flow 410 enters extrusion die 403. Extrusiondie 403 may be the same or substantially similar to that of extrusiondie 20 of FIG. 1. Within extrusion die 403, multilayer flow 410 isspread in the cross-web direction (x-direction) using a spreadingmanifold and then compressed in the y-direction to reduce the thicknessof multilayer flow 410. Each flow may be spread in the cross-webdirection substantially simultaneously with one another (as shown), maybe spread sequentially, or some combination thereof. Additionally, theflows may be spread and combined substantially simultaneously or may bespread and then combined sequentially.

FIG. 9 is a conceptual diagram illustrating a cross-sectional view ofmultilayer flow 410 in extrusion die 403 along cross-section C-C shownin FIG. 8. Multilayer flow 410 includes portions corresponding to firstpacket 400 and second packet 402 separated by core layer 408. First skinlayer 404 of multilayer flow 410 is on the opposite side of first packet400 from that of core layer 408. Similarly, second skin layer 406 ofmultilayer flow is on the opposite side of second packet 402 from thatof core layer 408.

Using the configuration of FIG. 8, packet combiner 401 may combine theindividual flows (first and second packets 400, 402, skin layers 404,406, and core layer 408) for each portion of multilayer flow 410 priorto being spread in the cross-web direction via extrusion die 403. Inother embodiments, packet combiner 401 and extrusion die 403 may beconfigured such that first multilayer packet 400, second multilayerpacket 402, first skin layer 404, second skin layer 406, and/or corelayer 408 are individually spread in the cross-web direction and thencombined together to form multilayer flow 410.

FIG. 10 is a conceptual diagram illustrating example packet transporter413 and extrusion die 415. Packet transporter 413 and extrusion die 415are configured such that first multilayer packet 412 and secondmultilayer packet 414 are spread in the cross-web direction prior tobeing combined with one another to form multilayer flow stream 416.Again, first multilayer packet 412 and second multilayer packet 414 maybe generated using any feedblock apparatus configuration describedherein, although any other suitable configuration capable of generatingtwo or more multilayer primary packets may also be used.

As shown in FIG. 10, packet transporter section 413 is not configured tocombine first multilayer packet 412 and second multilayer packet 414.Instead, packet transporter 413 defines the flows of first packet 412and second packet 414 such that the flows are maintained apart from oneanother within packet transporter 413 and delivered separately toextrusion die 415. The flows of packets 412, 414 both have asubstantially rectangular shape, the corners of which may be rounded,when entering extrusion die 415 that is defined by the width andthickness of the flow streams. Within extrusion die 415, both firstpacket 412 and second packer 414 are then spread in the cross-webdirection, e.g., via spreading manifolds of extrusion die 415, and mayalso be compressed in the y-direction. Such spreading and compressionchanges both the width and thickness of the flows prior to beingcombined with one another. After being spread individually in thecross-web direction within extrusion die 415, first and second packet412, 414 are combined with one another to form multilayer flow stream416.

Extrusion die 415 may be configured to sequentially or simultaneouslyspread packets 412 and 414. In some embodiments, first and secondpackets 412, 414 may be spread to substantially the same or differentdimension in the cross-web direction, i.e., first and second packets412, 414 may have substantially the same or different width after beingspread in the cross-web direction. In some embodiments, first and secondpackets 412, 414 may be spread within extrusion die 415 to a cross-webwidth desired for multilayer flow stream 416 to be further processed byone or more apparatuses downstream in film line 10 (FIG. 1).

In some examples, non-uniformities in the cross-web profile may bereduced by spreading first and second packets 412, 414 individuallyrather than after being combined with one another. In some cases, therapid rearrangement in the velocity profile once the flow streams ofmultiple packets, as well as any additional layer flows (e.g., a corelayer flow), are combined may contribute to non-uniformities in thecross-web profile of the final film produced in film line 10 (FIG. 1).In other cases, the potential for increased shear stress that resultscan make some layer structures vulnerable to flow instabilities that areinitiated when the flows streams are combined together, the degree ofwhich may depend on process conditions and/or polymeric resins that arebeing used to form the respective layers. Although flow channel geometrywithin a packet combining section for cases in which packets are notspread prior to being combined may be manipulated to address one or moreof the issues above, a configuration in which multilayer packets as wellas any additional layer flows are combined without being spread in thecross-web direction may limit cross-web layer uniformity, maximumprocess rates, and/or the thickness of an additional layer, such as, acore layer separating two packets.

By spreading first and second packets 412, 414, as well as anyadditional layers (such as, e.g., core layer 418 shown in FIG. 11), inthe cross-web direction prior to combining the respective flows,improved uniformity may result. For example, a separate spreadingmanifold may be used to spread each flow in the cross-web directionrather than using a single spreading manifold to spread the flow streamresulting from the combination of packets 412, 414, as well as anyadditional layers. As such, each separate manifold may be tailored toeach flow stream by taking into account material properties (e.g.,viscosity, elasticity, density) and process conditions (e.g., flow rate,temperature) that may be unique to each flow.

FIG. 11 is a conceptual diagram illustrating another example packettransporter 417 and extrusion die 419. Packet transporter 417 andextrusion die 419 may be similar to that of packet transporter 413 andextrusion die 415 of FIG. 10. For example, packet transporter 417 isconfigured to deliver first multilayer packet 412 to extrusion die 419separate from that of second multilayer packet 414, at which point firstpacket 412 and second packet 414 are separately spread in the cross-webdirection and then combined with one another to form a portion ofmultilayer flow stream 420.

However, unlike that shown in FIG. 10, packet transporter 417 alsodefines the flow of core layer 418. The composition of core layer 418may be substantially the same or similar to that of core layer 408 (FIG.8). As shown, core layer 418 is delivered by packet transporter 417 toextrusion die 419 between and separate from that of first packet 412 andsecond packet 414. Extrusion die 419 then spreads core layer 418 in thecross-web direction and also compresses core layer 418 in they-direction. Once reoriented, core layer 418 is combined with firstpacket 412 and second packet 414, each of which has also been spread inthe cross-web direction prior to being combined to form multilayer flowstream 420. First packet 412, second packet 414 and core layer 418 maybe combined within extrusion die 419 substantially simultaneously withone another (as shown in FIG. 11) or may be combined sequentially toform multilayer stream 420.

A configuration in which core layer 418 is spread in the cross-webdirection and then combined with first and second packets 412, 414 maybe used, for example, when core layer 418 is relatively thick and/orcomposed of material that is relatively difficult to coextrude. In FIG.11, the spreading manifold for core layer 418 may be tailoredspecifically to account for the specific rate and/or material propertiesof the core layer material. In this manner, a wider range of polymericresin material may be used to form core layer 418 compared to a case inwhich core layer 418 is coextruded with the flows of packets 412, 414.Such a configuration may address the potential to initiate flowinstabilities with elastic resins when flow streams are joined at highshear stress and/or extension rates. Similarly, such a configuration mayaddress undesirable layer rearrangement that may be caused by spreadingof multiple resins in the same manifold, and may be exacerbated by useof shear thinning resins.

FIG. 12 is a conceptual diagram illustrating a cross-sectional view ofmultilayer flow 420 in extrusion die 419 along cross-section D-D shownin FIG. 11. Multilayer flow 420 includes portions corresponding to firstpacket 412 and second packet 414 separated by core layer 418. In someexamples, core layer 418 may be inserted between first and secondpackets 412, 414 in multilayer flow stream 420 in cases in which packets412, 414 are intended to be separated from one another, e.g., in apost-tentering operation, to form two separate multilayer films fromsingle multilayer flow stream 420. In such examples, the core layermaterial may be selected to provide for a degree of adhesion to thefirst and second packets 412, 414 that allows for separation from corelayer 418 at some later point in time, e.g., prior to being wound onroll 26 (FIG. 1). In other examples, core layer 418 may be included toincrease the rigidity of manufactured film, e.g., beyond that providedby the combination of first and second packets 412, 414.

FIG. 13 is a conceptual diagram illustrating example packet transporter422 and extrusion die 424. Packet transporter 422 and extrusion die 424may be similar to that of packet transporter 413 and extrusion die 415of FIG. 10. In particular, packet transporter 422 is configured todeliver the flows of first multilayer packet 412, second multilayerpacket 414, core layer 418 separately from one another to extrusion die424. However, as shown in FIG. 13, packet transporter 422 also definesthe flow of first skin layer 404 and second skin layer 406 such thatfirst skin layer 404 and second skin layer 406 are combined with theflows of first packet 412 and second packet 414, respectively, prior tobeing delivered to extrusion die 424. Following the combination of skinlayers 404, 406 with first and second packets 412, 414, respectively,within packet transporter 422, the resulting flows enter extrusion die424 and are spread in the cross-web direction. In all, three separateflow streams enter extrusion die 424 (i.e., first packet 412/first skinlayer 404, core layer 418, and second packet 414/second skin layer 406),which are then each spread in the cross-web direction and combined withone another as illustrated in FIG. 13. In this manner, packettransporter 422 and extrusion die 424 are configured such that some ofthe various flow streams are combined with one another before beingspread in the cross-web direction and some of the flow streams arecombined after being spread in the cross-web direction.

FIG. 14 is a conceptual diagram illustrating an example cross-sectionalview of multilayer flow 426 in extrusion die 424 along cross-section E-Eshown in FIG. 13. Multilayer flow 426 includes portions corresponding tofirst packet 412 and second packet 414 separated by core layer 418.Multilayer flow 426 further includes portions corresponding to first andsecond skin layers 404, 406 combined with first and second packets 412,414, respectively, that form the outer layers of multilayer flow 426.

While the example multiple layer flows illustrated in FIGS. 9, 12, 14are substantially symmetrical with regard to skin layers 404, 406, otherexamples are contemplated. In some examples, a packet transporter may beconfigured such that a skin layer may be provided on only one side of amultilayer flow, more than one skin layer may be on any given side of amultilayer flow, and/or the same or different number of skin layers maybe on each side of a multilayer flow. Additionally, even when the numberof skin layers in a multilayer flow is symmetrical, the location in thez-direction at which each skin layer is added to the multilayer flow maybe the same or different from one another.

FIG. 15 is a conceptual diagram illustrating example packet transporter428 and extrusion die 430. Packet transporter 428 and extrusion die 430may be similar to that of packet transporter 417 and extrusion die 419of FIG. 11. For example, packet transporter 428 is configured to deliverfirst multilayer packet 412, second multilayer packet 414, and core flow418 to extrusion die 430 separate from one another. Within extrusion die430, first packet 412, second packet 414, and core layer 418 are thenseparately spread in the cross-web direction and then combined with oneanother to form portions of multilayer flow stream 436.

However, unlike that shown in FIG. 11, packet transporter 428 alsodefines the flow of first skin layer 432 and second skin layer 434. Thecomposition of first and second skin layers 432, 434 may besubstantially the same or similar to that of first and second skinlayers 404, 406, respectively, (FIGS. 8 and 13). As shown, the flows offirst and second skin layers 432, 434 are delivered by packettransporter 428 to extrusion die 430 separate from that of first packet412, second packet 414, and core layer 418. Extrusion die 430 thenspreads first and second skin layer 432, 434 in the cross-web directionand also compresses the layers in the y-direction in a manner similar tothat of first packet 412, second packet 414, and core layer 418. Oncespread in the cross-web direction, first packet 412, second packet 414,core layer 418, first skin layer 432, and second skin layer 434 are allcombined with each other to form multilayer flow stream 436. Firstpacket 412, second packet 414, core layer 418, first skin layer 432, andsecond skin layer 434 may be combined within extrusion die substantiallysimultaneously, sequentially, or some combination thereof to formmultilayer stream 436. In some examples, one or more of the flows forcore layer 418, first skin layer 432, and second skin layer 434 may beadded directly to extrusion die 430 rather than by way of transporter428.

FIGS. 16 and 17 are conceptual diagrams illustrating two examplecross-sectional views of multilayer flow 436 in extrusion die 430 alongcross-section F-F shown in FIG. 15. The general configuration ofmultilayer flow 436 shown in FIGS. 16 and 17 is substantially the sameas that of multilayer flow 426 show in FIG. 14. For example, theportions corresponding to first packet 412 and second packet 414 areseparated by core layer 418, and the portions corresponding to first andsecond skin layers 432, 434 are combined with first and second packets412, 414, respectively, to form the outer layers of multilayer flow 436.However, unlike multilayer flow 426 (FIG. 14), each portion (i.e., eachof first and second packets 412, 414, core flow 418, and first andsecond skin layers 432, 434) was separately spread in the cross-webdirection prior to being combined with one another to form multilayerflow 436. In this manner, the degree to which each of separate portionsof multilayer flow 436 are spread in the cross-web direction may beindividually controlled, thereby allowing for greater flexibility in howmuch each portion is spread within extrusion die 430 prior to beingcombined.

As shown in FIGS. 16 and 17, the thickness (y-direction) of each portion(i.e., the layers corresponding to each of first and second packets 412,414, core flow 418, and first and second skin layers 432, 434) may varywithin multilayer flow stream. FIG. 16 illustrates an example in whichcore layer 418 has a relatively small thickness compared to thethicknesses of first and second packets 412, 414 and first and secondskin layers 432, 434. Conversely, FIG. 17 illustrates an example inwhich core layer 418 has a relatively large thickness compared to thethicknesses of first and second packets 412, 414 and first and secondskin layers 432, 434. In FIG. 17, first and second skin layers 432, 434are also relatively thinner compared to that of the thicknesses of firstand second packet 412, 414.

In FIGS. 16 and 17, the thicknesses of first and second packets 412,414, core flow 418, and first and second skin layers 432, 434 inmultilayer flow 436 are symmetric about the center of core layer 418. Inother embodiments, the configuration of packet transporter 428 andextrusion die 430 may allow for an asymmetric thickness configuration offirst and second packets 412, 414, core flow 418, and first and secondskin layers 432, 434. For example, first packet 412 may have a thicknessthat is different from thickness of second packet 414 within multilayerflow 436. Additionally or alternatively, the thicknesses of first skinlayer 432 and second skin layer 434 may be different from one anotherwithin multilayer flow 436.

In any case, the thickness of the first and second packets 412, 414,core flow 418, and first and second skin layers 432, 434 may varyrelative to each other within multilayer flow 436. By individuallyspreading first and second packets 412, 414, core flow 418, and firstand second skin layers 432, 434 in the cross-web direction in extrusiondie 430, the thickness and cross-web width of the corresponding layerswithin multilayer flow 436 may be independently controlled. In thismanner, the thickness of each layer may be controlled as appropriate foreach layer within multilayer flow 436 such that the multilayer film orfilms generated from multilayer flow 436 exhibit one or more desiredproperties.

Various embodiments of the invention have been described. These andother embodiments are within the scope of the following claims.

1. A method for manufacturing a multilayer film using an assembly,wherein the assembly includes a primary packet creator section and anextrusion die including a first flow channel and a second flow channel,the method comprising: orienting, via the primary packet creatorsection, polymeric material to form a first primary packet including afirst plurality of polymeric layers stacked on each other and to form asecond primary packet including a second plurality of polymeric layersstacked on each other; receiving the first primary packet via the firstflow channel, the first primary packet including a first plurality ofpolymeric layers; receiving the second primary packet via the secondflow channel, the second packet including the second plurality ofpolymeric layers; spreading, via the extrusion die, at least one of thefirst primary packet and second primary packet in a cross-web directionto an extended width; and combining, via the extrusion die, the firstprimary packet and second primary packet with one another afterspreading at least one of the first packet and second packet in thecross-web direction to form a multilayer flow including the first andsecond plurality of polymeric layers.
 2. The method of claim 1, whereinthe first channel includes a first spreading manifold configured tospread the first primary packet in the cross-web direction and thesecond channel includes a second spreading manifold configured to spreadthe second primary packet in the cross-web direction.
 3. The method ofclaim 2, wherein the first and second spreading manifolds are formed byan extrusion die configured to combine the first and second primarypackets.
 4. The method of claim 1, further comprising: receiving anadditional layer flow via a third flow channel; and combining theadditional layer flow with the first and second primary packets to formthe multilayer flow stream.
 5. The method of claim 4, wherein theadditional layer flow comprises a core layer flow for forming a corelayer between the first and second primary packets in the multilayerflow stream.
 6. The method of claim 4, wherein the additional layer flowcomprises at least one skin layer flow for forming at least one skinlayer adjacent to at least one of the first packet or the second packetin the multilayer flow stream.
 7. The method of claim 4, furthercomprising combining the additional layer flow with at least one of thefirst primary packet or second primary packet prior to spreading the atleast one first primary packet or second primary packet in the cross-webdirection.
 8. The method of claim 4, further comprising spreading theadditional layer flow in the cross-web direction prior to combining theadditional layer flow with the first and second primary packets.
 9. Themethod of claim 1, further comprising: generating the first primarypacket via a first packet generator, the first primary packet having afirst cross-web width; generating the second primary packet via a secondpacket creator, the second packet having a second cross-web width,wherein receiving the first primary packet via the first flow channelcomprises receiving the first packet having the first cross-web widthvia the first flow channel, and receiving the second primary packet viathe second flow channel comprises receiving the second packet having thesecond cross-web width via the second flow channel, and whereinspreading the at least one of the first primary packet and secondprimary packet in a cross-web direction comprising spreading the firstprimary packet to a third cross-web width greater than the firstcross-web width and spreading the second primary packet to a fourthcross-web width greater than the second cross-web width.
 10. The methodof claim 1, wherein the first and second packets have substantially thesame cross-web width when combined with one another.
 11. The method ofclaim 1, further comprising manufacturing the multilayer flow streaminto a multilayer optical film.